Retire the classic flight screen and stop the start-up location grant being dropped

MainActivity now makes the app's only start-up permission request and tells
Dart when it finishes; the phone-location stream waits for that instead of
asking in parallel, which made Android drop the location grant.

The P3 simulator run passed, so the pre-P2 FlightControlPage, the pages only
it used and its Settings toggle are gone. The app smoke test checks the home
screen again instead of the login gate removed in July.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Fly App/test/widget_test.dart

@@ -1,13 +1,17 @@
+import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
 import 'package:pilotvault_fly/main.dart';
 
 void main() {
-  testWidgets('Shows the login screen when signed out',
-      (WidgetTester tester) async {
+  testWidgets('Opens on the home screen with no aircraft connected', (WidgetTester tester) async {
+    SharedPreferences.setMockInitialValues(<String, Object>{});
     await tester.pumpWidget(const DjiSampleApp());
+    await tester.pump();
 
-    expect(find.text('Sign in'), findsWidgets);
-    expect(find.text('Sign in to continue'), findsOneWidget);
+    expect(find.text('No aircraft connected'), findsOneWidget);
+    expect(find.text('Connect aircraft'), findsOneWidget);
+    expect(find.byType(MaterialApp), findsOneWidget);
   });
 }