Fix bugs across app + server, optimize UI/UX, add Gitea CI

Bug fixes (Flutter):
- Wrap multi-statement DB writes (insert/update/delete note, deleteDocument,
  deletePageData, OCR FTS merge, migrations) in transactions to prevent data
  loss on interruption and a read-modify-write FTS race.
- Fix PdfDocument leaks on exception (try/finally dispose) and preserve image
  aspect ratio when stamping images onto PDF pages.
- Guard file-picker against empty selection (was .single -> crash).
- Fix eraser ConcurrentModificationError and unmodifiable-list crash on PDF
  pages; capture page synchronously on save to stop wrong-page data loss.
- Fix Riverpod DB-not-ready races, broken pull-to-refresh, settings load race,
  and search N+1; transform stored annotations on PDF page rotation.
- Normalize pen pressure for devices without a pressure range.
- PPT: single source of truth for slide strokes so ink displays and exports.

UI/UX:
- Material 3 typography, theme-aware colors (dark-mode fixes), hover cursors
  and right-click/visible actions on desktop, keyboard shortcuts (undo/redo/
  save/find), toolbar overflow handling, friendlier empty states, semantic OCR
  status badges, relative timestamps, 1-based page indicators, large-deck PPT
  navigation, and a scratchpad-scope label in split view.

Server (optional backend):
- Persist JWT secret (was per-process random), block path traversal in storage,
  fix CORS '*'+credentials, add OCR job ownership checks, last-writer-wins sync
  guard, constant-time login, and split out heavy OCR deps so the API/tests run
  without them.

CI: Gitea workflows for format+analyze+test (Linux, system sqlite) and a
Windows release build; pristine `flutter analyze`, all Flutter and server tests
green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/main.dart

@@ -0,0 +1,55 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:google_fonts/google_fonts.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'providers/settings_provider.dart';
+import 'screens/home_screen.dart';
+import 'services/database_service.dart';
+
+Future<void> main() async {
+  WidgetsFlutterBinding.ensureInitialized();
+
+  // Ensure DB is ready before the app starts so providers can use it eagerly
+  await DatabaseService.getInstance();
+
+  // Initialize SharedPreferences
+  await SharedPreferences.getInstance();
+
+  runApp(const ProviderScope(child: BadNoteApp()));
+}
+
+class BadNoteApp extends ConsumerWidget {
+  const BadNoteApp({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final settings = ref.watch(settingsProvider);
+
+    return MaterialApp(
+      title: 'BadNote',
+      themeMode: settings.themeMode,
+      theme: ThemeData(
+        colorScheme: ColorScheme.fromSeed(
+          seedColor: settings.colorSchemeSeed,
+          brightness: Brightness.light,
+        ),
+        textTheme: GoogleFonts.interTextTheme(
+          ThemeData(brightness: Brightness.light).textTheme,
+        ),
+        useMaterial3: true,
+      ),
+      darkTheme: ThemeData(
+        colorScheme: ColorScheme.fromSeed(
+          seedColor: settings.colorSchemeSeed,
+          brightness: Brightness.dark,
+        ),
+        textTheme: GoogleFonts.interTextTheme(
+          ThemeData(brightness: Brightness.dark).textTheme,
+        ),
+        useMaterial3: true,
+      ),
+      home: const HomeScreen(),
+    );
+  }
+}