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/settings_dao.g.dart

@@ -0,0 +1,16 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'settings_dao.dart';
+
+// ignore_for_file: type=lint
+mixin _$SettingsDaoMixin on DatabaseAccessor<AppDatabase> {
+  $UserSettingsTable get userSettings => attachedDatabase.userSettings;
+  SettingsDaoManager get managers => SettingsDaoManager(this);
+}
+
+class SettingsDaoManager {
+  final _$SettingsDaoMixin _db;
+  SettingsDaoManager(this._db);
+  $$UserSettingsTableTableManager get userSettings =>
+      $$UserSettingsTableTableManager(_db.attachedDatabase, _db.userSettings);
+}