feat: set up Flutter project with drift database, Riverpod providers, and LLM service layer

- Configure dependencies: drift 2.32.x, flutter_riverpod 3.3.1, fl_chart 1.2.x,
  flutter_local_notifications 21.x, local_auth 3.x, and supporting packages
- Drop riverpod_generator (incompatible analyzer version with drift_dev 2.32.x);
  convert all providers to manual Riverpod 3.x API using Notifier<T> and typed families
- Define drift schema: MoodEntries, Activities, EntryActivities, Tags, EntryTags,
  LlmInsights, UserSettings with four DAOs (mood, activity, insight, settings)
- Add LLM service abstraction (LlmService) and MediaPipe implementation
- Fix SettingsDao.delete → deleteByKey to avoid shadowing drift's inherited delete method

lib/core/providers/mood_provider.dart

@@ -0,0 +1,103 @@
+import 'package:drift/drift.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../database/app_database.dart';
+import 'database_provider.dart';
+
+// ── All entries stream ────────────────────────────────────────────────────────
+
+final moodEntriesProvider = StreamProvider.autoDispose<List<MoodEntry>>((ref) {
+  return ref.watch(moodDaoProvider).watchAllEntries();
+});
+
+// ── Entries for a specific day ────────────────────────────────────────────────
+
+final moodEntriesForDayProvider =
+    StreamProvider.autoDispose.family<List<MoodEntry>, DateTime>((ref, day) {
+  return ref.watch(moodDaoProvider).watchEntriesForDay(day);
+});
+
+// ── Daily averages for calendar heatmap ──────────────────────────────────────
+
+final dailyAveragesProvider = FutureProvider.autoDispose
+    .family<Map<DateTime, double>, ({DateTime start, DateTime end})>(
+  (ref, range) =>
+      ref.watch(moodDaoProvider).getDailyAverages(range.start, range.end),
+);
+
+// ── Selected day (drives calendar + day detail) ───────────────────────────────
+
+class SelectedDay extends Notifier<DateTime> {
+  @override
+  DateTime build() => DateTime.now();
+
+  void select(DateTime day) {
+    state = DateTime(day.year, day.month, day.day);
+  }
+
+  void selectToday() {
+    final now = DateTime.now();
+    state = DateTime(now.year, now.month, now.day);
+  }
+}
+
+final selectedDayProvider =
+    NotifierProvider.autoDispose<SelectedDay, DateTime>(SelectedDay.new);
+
+// ── Mood entry notifier (create / update / delete) ────────────────────────────
+
+class MoodEntryNotifier extends Notifier<AsyncValue<void>> {
+  @override
+  AsyncValue<void> build() => const AsyncData(null);
+
+  Future<void> addEntry({
+    required int moodLevel,
+    String? note,
+    List<int> activityIds = const [],
+    List<int> tagIds = const [],
+    DateTime? timestamp,
+  }) async {
+    state = const AsyncLoading();
+    state = await AsyncValue.guard(() async {
+      final dao = ref.read(moodDaoProvider);
+      await dao.insertEntryWithActivities(
+        entry: MoodEntriesCompanion.insert(
+          moodLevel: moodLevel,
+          timestamp: timestamp ?? DateTime.now(),
+          note: Value(note),
+        ),
+        activityIds: activityIds,
+        tagIds: tagIds,
+      );
+    });
+  }
+
+  Future<void> deleteEntry(int id) async {
+    state = const AsyncLoading();
+    state = await AsyncValue.guard(
+      () => ref.read(moodDaoProvider).deleteEntry(id),
+    );
+  }
+
+  Future<void> updateEntry({
+    required int id,
+    required int moodLevel,
+    String? note,
+    DateTime? timestamp,
+  }) async {
+    state = const AsyncLoading();
+    state = await AsyncValue.guard(
+      () => ref.read(moodDaoProvider).updateEntry(
+            MoodEntriesCompanion(
+              id: Value(id),
+              moodLevel: Value(moodLevel),
+              note: Value(note),
+              timestamp: Value(timestamp ?? DateTime.now()),
+            ),
+          ),
+    );
+  }
+}
+
+final moodEntryNotifierProvider =
+    NotifierProvider.autoDispose<MoodEntryNotifier, AsyncValue<void>>(
+        MoodEntryNotifier.new);