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/settings_provider.dart

@@ -0,0 +1,69 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'database_provider.dart';
+
+// ── Key constants ─────────────────────────────────────────────────────────────
+
+abstract class SettingsKeys {
+  static const reminderEnabled = 'reminder_enabled';
+  static const reminderTime = 'reminder_time'; // stored as 'HH:mm'
+  static const biometricEnabled = 'biometric_enabled';
+  static const themMode = 'theme_mode'; // 'system' | 'light' | 'dark'
+  static const modelDownloaded = 'model_downloaded';
+  static const onboardingComplete = 'onboarding_complete';
+}
+
+// ── Generic setting reader ────────────────────────────────────────────────────
+
+final settingProvider =
+    FutureProvider.autoDispose.family<String?, String>((ref, key) {
+  return ref.watch(settingsDaoProvider).get(key);
+});
+
+// ── Settings notifier ─────────────────────────────────────────────────────────
+
+class SettingsNotifier extends Notifier<AsyncValue<void>> {
+  @override
+  AsyncValue<void> build() => const AsyncData(null);
+
+  Future<void> set(String key, String value) async {
+    await ref.read(settingsDaoProvider).set(key, value);
+    ref.invalidate(settingProvider(key));
+  }
+
+  Future<void> setReminderEnabled(bool enabled) =>
+      set(SettingsKeys.reminderEnabled, enabled.toString());
+
+  Future<void> setReminderTime(int hour, int minute) => set(
+      SettingsKeys.reminderTime,
+      '${hour.toString().padLeft(2, '0')}:${minute.toString().padLeft(2, '0')}');
+
+  Future<void> setBiometricEnabled(bool enabled) =>
+      set(SettingsKeys.biometricEnabled, enabled.toString());
+
+  Future<void> setThemeMode(String mode) => set(SettingsKeys.themMode, mode);
+
+  Future<void> markModelDownloaded() =>
+      set(SettingsKeys.modelDownloaded, 'true');
+
+  Future<void> markOnboardingComplete() =>
+      set(SettingsKeys.onboardingComplete, 'true');
+}
+
+final settingsNotifierProvider =
+    NotifierProvider.autoDispose<SettingsNotifier, AsyncValue<void>>(
+        SettingsNotifier.new);
+
+// ── Convenience bool readers ──────────────────────────────────────────────────
+
+final isOnboardingCompleteProvider =
+    FutureProvider.autoDispose<bool>((ref) async {
+  final val =
+      await ref.watch(settingProvider(SettingsKeys.onboardingComplete).future);
+  return val == 'true';
+});
+
+final isModelDownloadedProvider = FutureProvider.autoDispose<bool>((ref) async {
+  final val =
+      await ref.watch(settingProvider(SettingsKeys.modelDownloaded).future);
+  return val == 'true';
+});