feat: implement history screen with calendar heatmap and day detail

Adds a month grid heatmap (colour-coded by daily mood average), prev/next
month navigation, and a scrollable entry list below for the selected day
showing mood, time, note, and metric chips (sleep, energy, positivity,
self-worth).

lib/features/calendar/calendar_screen.dart

@@ -1,12 +1,150 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../core/providers/mood_provider.dart';
+import 'widgets/calendar_heatmap.dart';
+import 'widgets/day_entry_card.dart';
 
-class CalendarScreen extends StatelessWidget {
+const _months = [
+  'January', 'February', 'March', 'April', 'May', 'June',
+  'July', 'August', 'September', 'October', 'November', 'December',
+];
+
+class CalendarScreen extends ConsumerStatefulWidget {
   const CalendarScreen({super.key});
 
+  @override
+  ConsumerState<CalendarScreen> createState() => _CalendarScreenState();
+}
+
+class _CalendarScreenState extends ConsumerState<CalendarScreen> {
+  late DateTime _month;
+
+  @override
+  void initState() {
+    super.initState();
+    final now = DateTime.now();
+    _month = DateTime(now.year, now.month);
+  }
+
+  void _prevMonth() => setState(() => _month = DateTime(_month.year, _month.month - 1));
+
+  void _nextMonth() {
+    final now = DateTime.now();
+    final next = DateTime(_month.year, _month.month + 1);
+    if (!next.isAfter(DateTime(now.year, now.month))) {
+      setState(() => _month = next);
+    }
+  }
+
+  bool get _canGoForward {
+    final now = DateTime.now();
+    return _month.year < now.year ||
+        (_month.year == now.year && _month.month < now.month);
+  }
+
   @override
   Widget build(BuildContext context) {
-    return const Scaffold(
+    final selectedDay = ref.watch(selectedDayProvider);
-      body: Center(child: Text('History coming soon')),
+    final entriesAsync = ref.watch(moodEntriesForDayProvider(selectedDay));
+
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('History'),
+        centerTitle: false,
+      ),
+      body: Column(
+        children: [
+          _MonthNav(
+            label: '${_months[_month.month - 1]} ${_month.year}',
+            onPrev: _prevMonth,
+            onNext: _canGoForward ? _nextMonth : null,
+          ),
+          CalendarHeatmap(
+            month: _month,
+            selectedDay: selectedDay,
+            onDayTap: (day) {
+              ref.read(selectedDayProvider.notifier).select(day);
+              // Follow the selected day's month
+              final m = DateTime(day.year, day.month);
+              if (m != _month) setState(() => _month = m);
+            },
+          ),
+          const Divider(height: 1),
+          Expanded(
+            child: entriesAsync.when(
+              data: (entries) => entries.isEmpty
+                  ? _EmptyDay(day: selectedDay)
+                  : ListView.builder(
+                      padding: const EdgeInsets.symmetric(vertical: 8),
+                      itemCount: entries.length,
+                      itemBuilder: (context, i) =>
+                          DayEntryCard(entry: entries[i]),
+                    ),
+              loading: () =>
+                  const Center(child: CircularProgressIndicator()),
+              error: (_, __) => const SizedBox.shrink(),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _MonthNav extends StatelessWidget {
+  const _MonthNav({
+    required this.label,
+    required this.onPrev,
+    required this.onNext,
+  });
+
+  final String label;
+  final VoidCallback onPrev;
+  final VoidCallback? onNext;
+
+  @override
+  Widget build(BuildContext context) {
+    return Padding(
+      padding: const EdgeInsets.symmetric(horizontal: 4),
+      child: Row(
+        children: [
+          IconButton(icon: const Icon(Icons.chevron_left), onPressed: onPrev),
+          Expanded(
+            child: Text(
+              label,
+              textAlign: TextAlign.center,
+              style: Theme.of(context).textTheme.titleMedium,
+            ),
+          ),
+          IconButton(
+            icon: const Icon(Icons.chevron_right),
+            onPressed: onNext,
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _EmptyDay extends StatelessWidget {
+  const _EmptyDay({required this.day});
+
+  final DateTime day;
+
+  @override
+  Widget build(BuildContext context) {
+    final now = DateTime.now();
+    final today = DateTime(now.year, now.month, now.day);
+    final label = day == today ? 'today' : '${day.day}/${day.month}/${day.year}';
+
+    return Center(
+      child: Text(
+        'No entries for $label',
+        style: Theme.of(context)
+            .textTheme
+            .bodyMedium
+            ?.copyWith(color: Theme.of(context).colorScheme.outline),
+      ),
     );
   }
 }

lib/features/calendar/widgets/calendar_heatmap.dart

@@ -0,0 +1,142 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../core/providers/mood_provider.dart';
+
+const _moodColors = [
+  Color(0xFFE57373),
+  Color(0xFFFFB74D),
+  Color(0xFFFFD54F),
+  Color(0xFF81C784),
+  Color(0xFF4DB6AC),
+];
+
+class CalendarHeatmap extends ConsumerWidget {
+  const CalendarHeatmap({
+    super.key,
+    required this.month,
+    required this.selectedDay,
+    required this.onDayTap,
+  });
+
+  final DateTime month;
+  final DateTime selectedDay;
+  final ValueChanged<DateTime> onDayTap;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final start = DateTime(month.year, month.month, 1);
+    final end = DateTime(month.year, month.month + 1, 0, 23, 59, 59);
+    final averagesAsync =
+        ref.watch(dailyAveragesProvider((start: start, end: end)));
+
+    return averagesAsync.when(
+      data: (averages) => _HeatmapGrid(
+        month: month,
+        averages: averages,
+        selectedDay: selectedDay,
+        onDayTap: onDayTap,
+      ),
+      loading: () =>
+          const SizedBox(height: 280, child: Center(child: CircularProgressIndicator())),
+      error: (_, __) => const SizedBox(height: 280),
+    );
+  }
+}
+
+class _HeatmapGrid extends StatelessWidget {
+  const _HeatmapGrid({
+    required this.month,
+    required this.averages,
+    required this.selectedDay,
+    required this.onDayTap,
+  });
+
+  final DateTime month;
+  final Map<DateTime, double> averages;
+  final DateTime selectedDay;
+  final ValueChanged<DateTime> onDayTap;
+
+  @override
+  Widget build(BuildContext context) {
+    final cs = Theme.of(context).colorScheme;
+    final daysInMonth = DateTime(month.year, month.month + 1, 0).day;
+    final leadingBlanks = DateTime(month.year, month.month, 1).weekday - 1;
+    final today = DateTime.now();
+    final todayNorm = DateTime(today.year, today.month, today.day);
+
+    return Padding(
+      padding: const EdgeInsets.fromLTRB(16, 4, 16, 16),
+      child: Column(
+        children: [
+          Row(
+            children: ['Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa', 'Su']
+                .map((l) => Expanded(
+                      child: Center(
+                        child: Text(
+                          l,
+                          style: Theme.of(context)
+                              .textTheme
+                              .labelSmall
+                              ?.copyWith(color: cs.outline),
+                        ),
+                      ),
+                    ))
+                .toList(),
+          ),
+          const SizedBox(height: 6),
+          GridView.builder(
+            shrinkWrap: true,
+            physics: const NeverScrollableScrollPhysics(),
+            gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+              crossAxisCount: 7,
+              mainAxisSpacing: 4,
+              crossAxisSpacing: 4,
+            ),
+            itemCount: leadingBlanks + daysInMonth,
+            itemBuilder: (context, i) {
+              if (i < leadingBlanks) return const SizedBox.shrink();
+              final day = i - leadingBlanks + 1;
+              final date = DateTime(month.year, month.month, day);
+              final avg = averages[date];
+              final isSelected = date == selectedDay;
+              final isToday = date == todayNorm;
+
+              Color? fill;
+              if (avg != null) {
+                final idx = (avg.clamp(1.0, 5.0) - 1).round().clamp(0, 4);
+                fill = _moodColors[idx].withValues(alpha: 0.85);
+              }
+
+              return GestureDetector(
+                onTap: () => onDayTap(date),
+                child: Container(
+                  decoration: BoxDecoration(
+                    shape: BoxShape.circle,
+                    color: fill ??
+                        cs.surfaceContainerHighest.withValues(alpha: 0.5),
+                    border: isSelected
+                        ? Border.all(color: cs.primary, width: 2.5)
+                        : isToday
+                            ? Border.all(color: cs.outline, width: 1)
+                            : null,
+                  ),
+                  child: Center(
+                    child: Text(
+                      '$day',
+                      style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                            color: fill != null ? Colors.white : cs.onSurfaceVariant,
+                            fontWeight: isSelected || isToday
+                                ? FontWeight.bold
+                                : FontWeight.normal,
+                          ),
+                    ),
+                  ),
+                ),
+              );
+            },
+          ),
+        ],
+      ),
+    );
+  }
+}

lib/features/calendar/widgets/day_entry_card.dart

@@ -0,0 +1,137 @@
+import 'package:flutter/material.dart';
+import '../../../core/database/app_database.dart';
+
+const _moodEmojis = ['😞', '😔', '😐', '🙂', '😄'];
+const _moodLabels = ['Awful', 'Bad', 'Okay', 'Good', 'Great'];
+
+class DayEntryCard extends StatelessWidget {
+  const DayEntryCard({super.key, required this.entry});
+
+  final MoodEntry entry;
+
+  @override
+  Widget build(BuildContext context) {
+    final idx = (entry.moodLevel - 1).clamp(0, 4);
+
+    return Card(
+      margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 4),
+      child: Padding(
+        padding: const EdgeInsets.all(12),
+        child: Row(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Text(_moodEmojis[idx], style: const TextStyle(fontSize: 28)),
+            const SizedBox(width: 12),
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Row(
+                    children: [
+                      Text(_moodLabels[idx],
+                          style: Theme.of(context).textTheme.titleSmall),
+                      const Spacer(),
+                      Text(
+                        _formatTime(entry.timestamp),
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                              color: Theme.of(context).colorScheme.outline,
+                            ),
+                      ),
+                    ],
+                  ),
+                  if (entry.note != null && entry.note!.isNotEmpty) ...[
+                    const SizedBox(height: 4),
+                    Text(
+                      entry.note!,
+                      style: Theme.of(context).textTheme.bodySmall,
+                      maxLines: 2,
+                      overflow: TextOverflow.ellipsis,
+                    ),
+                  ],
+                  if (_hasMetrics) ...[
+                    const SizedBox(height: 8),
+                    _MetricsRow(entry: entry),
+                  ],
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  bool get _hasMetrics =>
+      entry.sleepMinutes != null ||
+      entry.energyLevel != null ||
+      entry.positivityLevel != null ||
+      entry.selfWorthLevel != null;
+
+  static String _formatTime(DateTime dt) {
+    final h = dt.hour.toString().padLeft(2, '0');
+    final m = dt.minute.toString().padLeft(2, '0');
+    return '$h:$m';
+  }
+}
+
+class _MetricsRow extends StatelessWidget {
+  const _MetricsRow({required this.entry});
+
+  final MoodEntry entry;
+
+  @override
+  Widget build(BuildContext context) {
+    return Wrap(
+      spacing: 6,
+      runSpacing: 4,
+      children: [
+        if (entry.sleepMinutes != null)
+          _Chip(
+            icon: Icons.bedtime_outlined,
+            label: _sleepLabel(entry.sleepMinutes!),
+          ),
+        if (entry.energyLevel != null)
+          _Chip(label: ['💤', '🥱', '⚡', '🔥', '🚀'][(entry.energyLevel! - 1).clamp(0, 4)]),
+        if (entry.positivityLevel != null)
+          _Chip(label: ['🌧', '☁️', '🌤', '☀️', '🌈'][(entry.positivityLevel! - 1).clamp(0, 4)]),
+        if (entry.selfWorthLevel != null)
+          _Chip(label: ['💔', '😕', '😐', '💪', '⭐'][(entry.selfWorthLevel! - 1).clamp(0, 4)]),
+      ],
+    );
+  }
+
+  static String _sleepLabel(int minutes) {
+    final h = minutes ~/ 60;
+    final m = (minutes % 60).toString().padLeft(2, '0');
+    return '$h:$m';
+  }
+}
+
+class _Chip extends StatelessWidget {
+  const _Chip({this.icon, required this.label});
+
+  final IconData? icon;
+  final String label;
+
+  @override
+  Widget build(BuildContext context) {
+    final cs = Theme.of(context).colorScheme;
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 3),
+      decoration: BoxDecoration(
+        color: cs.surfaceContainerHighest,
+        borderRadius: BorderRadius.circular(12),
+      ),
+      child: Row(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          if (icon != null) ...[
+            Icon(icon, size: 12, color: cs.outline),
+            const SizedBox(width: 3),
+          ],
+          Text(label, style: Theme.of(context).textTheme.labelSmall),
+        ],
+      ),
+    );
+  }
+}