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/database/daos/mood_dao.dart

@@ -0,0 +1,92 @@
+import 'package:drift/drift.dart';
+import '../app_database.dart';
+import '../tables.dart';
+
+part 'mood_dao.g.dart';
+
+// Joined result — entry + its activities
+class MoodEntryWithActivities {
+  final MoodEntry entry;
+  final List<Activity> activities;
+  final List<Tag> tags;
+  MoodEntryWithActivities({
+    required this.entry,
+    required this.activities,
+    required this.tags,
+  });
+}
+
+@DriftAccessor(
+    tables: [MoodEntries, EntryActivities, Activities, EntryTags, Tags])
+class MoodDao extends DatabaseAccessor<AppDatabase> with _$MoodDaoMixin {
+  MoodDao(super.db);
+
+  // ── Writes ──────────────────────────────────────────────────────────────────
+
+  Future<int> insertEntry(MoodEntriesCompanion entry) =>
+      into(moodEntries).insert(entry);
+
+  Future<void> insertEntryWithActivities({
+    required MoodEntriesCompanion entry,
+    required List<int> activityIds,
+    required List<int> tagIds,
+  }) async {
+    await transaction(() async {
+      final entryId = await into(moodEntries).insert(entry);
+      for (final actId in activityIds) {
+        await into(entryActivities).insert(
+          EntryActivitiesCompanion.insert(entryId: entryId, activityId: actId),
+        );
+      }
+      for (final tagId in tagIds) {
+        await into(entryTags).insert(
+          EntryTagsCompanion.insert(entryId: entryId, tagId: tagId),
+        );
+      }
+    });
+  }
+
+  Future<void> deleteEntry(int id) =>
+      (delete(moodEntries)..where((t) => t.id.equals(id))).go();
+
+  Future<void> updateEntry(MoodEntriesCompanion entry) =>
+      (update(moodEntries)..where((t) => t.id.equals(entry.id.value)))
+          .write(entry);
+
+  // ── Reads ───────────────────────────────────────────────────────────────────
+
+  Stream<List<MoodEntry>> watchAllEntries() =>
+      (select(moodEntries)..orderBy([(t) => OrderingTerm.desc(t.timestamp)]))
+          .watch();
+
+  Stream<List<MoodEntry>> watchEntriesForDay(DateTime day) {
+    final start = DateTime(day.year, day.month, day.day);
+    final end = start.add(const Duration(days: 1));
+    return (select(moodEntries)
+          ..where((t) => t.timestamp.isBetweenValues(start, end))
+          ..orderBy([(t) => OrderingTerm.desc(t.timestamp)]))
+        .watch();
+  }
+
+  Future<List<MoodEntry>> getEntriesInRange(DateTime start, DateTime end) =>
+      (select(moodEntries)
+            ..where((t) => t.timestamp.isBetweenValues(start, end))
+            ..orderBy([(t) => OrderingTerm.asc(t.timestamp)]))
+          .get();
+
+  // Average mood per day — used by calendar heatmap
+  Future<Map<DateTime, double>> getDailyAverages(
+      DateTime start, DateTime end) async {
+    final entries = await getEntriesInRange(start, end);
+    final Map<DateTime, List<int>> grouped = {};
+    for (final e in entries) {
+      final day =
+          DateTime(e.timestamp.year, e.timestamp.month, e.timestamp.day);
+      grouped.putIfAbsent(day, () => []).add(e.moodLevel);
+    }
+    return grouped.map(
+      (day, levels) =>
+          MapEntry(day, levels.reduce((a, b) => a + b) / levels.length),
+    );
+  }
+}