feat: wire up app shell, log mood screen, and fix Android build

- Bootstrap ProviderScope in main.dart and move App to app.dart with light/dark theming
- Add initial LogMoodScreen with mood entry flow and shared activity/mood widgets
- Add kIsWeb guard in app_database.dart for drift web support
- Enable Android core library desugaring required by flutter_local_notifications 21.x
- Guard all async notifier state assignments with ref.mounted checks to prevent
  use-after-dispose errors when providers are auto-disposed mid-operation

lib/core/database/app_database.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import 'package:drift/drift.dart';
 import 'package:drift_flutter/drift_flutter.dart';
 import 'package:path_provider/path_provider.dart';
@@ -84,6 +85,15 @@ class AppDatabase extends _$AppDatabase {
 }
 
 QueryExecutor _openConnection() {
+  if (kIsWeb) {
+    return driftDatabase(
+      name: 'lumina_db',
+      web: DriftWebOptions(
+        sqlite3Wasm: Uri.parse('sqlite3.wasm'),
+        driftWorker: Uri.parse('drift_worker.dart.js'),
+      ),
+    );
+  }
   return driftDatabase(
     name: 'lumina_db',
     native: DriftNativeOptions(