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/domain/mission/mission.dart

@@ -0,0 +1,24 @@
+import '../waypoint/flat_waypoint_list.dart';
+
+/// Strategy-Pattern fuer erweiterbare Missionstypen (Architektur-Doku 3.2).
+abstract class Mission {
+  String get name;
+
+  FlatWaypointList toFlatWaypointList();
+}
+
+/// Wegpunkt-Streckenmission - aktuell einziger implementierter Missionstyp.
+class TrackMission implements Mission {
+  const TrackMission({required this.name, required this.waypoints});
+
+  @override
+  final String name;
+
+  final List<Waypoint> waypoints;
+
+  @override
+  FlatWaypointList toFlatWaypointList() => FlatWaypointList(waypoints);
+}
+
+// SurveyAreaMission (Flaechenabflug) und SearchAreaMission (Suchmuster) sind
+// im Strategy-Pattern vorgesehen, aber noch nicht spezifiziert (Doku 6).