Add Flutter project skeleton (Android-only MVP)

Five-layer architecture per DMC_Architektur_und_Design.md: FlightControllerLink
abstraction (Mock + MSP stub), protocol-neutral mission domain layer, App-Mode
state machine with Ready-to-Fly gate, Drift persistence schema, and placeholder
UI screens wired via go_router. App icon generated from design/Y2_pink_dark.svg.
Verified with flutter analyze and flutter test.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/lib/main.dart

@@ -0,0 +1,55 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
+
+import 'app_mode/app_mode_cubit.dart';
+import 'ui/app_shell.dart';
+import 'ui/dmc_colors.dart';
+import 'ui/screens/library/library_screen.dart';
+import 'ui/screens/settings/settings_screen.dart';
+
+void main() {
+  runApp(const DmcApp());
+}
+
+final _router = GoRouter(
+  routes: [
+    GoRoute(path: '/', builder: (context, state) => const AppShell()),
+    GoRoute(
+      path: '/settings',
+      builder: (context, state) => const SettingsScreen(),
+    ),
+    GoRoute(
+      path: '/library',
+      builder: (context, state) => const LibraryScreen(),
+    ),
+  ],
+);
+
+class DmcApp extends StatelessWidget {
+  const DmcApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return ProviderScope(
+      child: BlocProvider(
+        create: (_) => AppModeCubit(),
+        child: MaterialApp.router(
+          title: 'Drone Mission Control',
+          debugShowCheckedModeBanner: false,
+          theme: ThemeData(
+            useMaterial3: true,
+            brightness: Brightness.dark,
+            scaffoldBackgroundColor: const Color(0xFF0F0F0F),
+            colorScheme: ColorScheme.fromSeed(
+              seedColor: DmcColors.setBlue,
+              brightness: Brightness.dark,
+            ),
+          ),
+          routerConfig: _router,
+        ),
+      ),
+    );
+  }
+}