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/services/database/app_database.dart

@@ -0,0 +1,39 @@
+import 'dart:io';
+
+import 'package:drift/drift.dart';
+import 'package:drift/native.dart';
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
+
+part 'app_database.g.dart';
+
+/// Persistenz fuer Missionen (Architektur-Doku 4.15): Drift statt Hive, weil
+/// indexierte Abfragen (Suche nach Name/Ort/Datum) benoetigt werden und das
+/// Schema kompatibel zu einem kuenftigen lokal-first Server-Sync-Muster
+/// (Dirty-Flags, Server-IDs) bleiben soll.
+class Missions extends Table {
+  IntColumn get id => integer().autoIncrement()();
+  TextColumn get name => text()();
+  TextColumn get location => text().nullable()();
+  DateTimeColumn get createdAt =>
+      dateTime().withDefault(currentDateAndTime)();
+  TextColumn get waypointsJson => text()();
+  BoolColumn get isDirty => boolean().withDefault(const Constant(true))();
+  TextColumn get serverId => text().nullable()();
+}
+
+@DriftDatabase(tables: [Missions])
+class AppDatabase extends _$AppDatabase {
+  AppDatabase() : super(_openConnection());
+
+  @override
+  int get schemaVersion => 1;
+
+  static LazyDatabase _openConnection() {
+    return LazyDatabase(() async {
+      final dbFolder = await getApplicationDocumentsDirectory();
+      final file = File(p.join(dbFolder.path, 'dmc_missions.sqlite'));
+      return NativeDatabase.createInBackground(file);
+    });
+  }
+}