build: upgrade to Flutter 3.47.4 (AGP 9.1 / Gradle 9.3, iOS 15 + UIScene), refresh deps and CI

Flutter 3.24.5 -> 3.47.4 with the matching toolchain changes:

- pubspec: Dart ^3.11, Firebase core 4 / auth 6 / firestore 6 / storage 13,
  drop unused image_cropper, logging, change_app_package_name,
  pdf_widget_wrapper; pin path_provider_android <2.3 (needs NDK/CMake, not
  feasible on the ARM64 Gitea runner)
- Dart: CardTheme -> CardThemeData, replace deprecated withOpacity,
  Matrix4.scale, DropdownButtonFormField.value
- iOS: deployment target 15.0, UIScene lifecycle (AppDelegate/Info.plist),
  untrack stale Podfile.lock, add LaunchImage asset set
- Android: Gradle 9.3.1, AGP 9.1.0, Kotlin 2.4.0, google-services 4.5.0,
  layout.buildDirectory instead of removed Project.buildDir, remove manifest
  package attribute and duplicate MainActivity, kotlin.incremental=false
- CI: pin FLUTTER_VERSION in both workflows; iOS on macos-26 with SwiftPM
  disabled (CocoaPods only); Gitea job keeps cirruslabs 3.44.0 as base image
  (images discontinued) and switches the bundled Flutter SDK by git tag

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

lib/screens/pdf_viewer_screen.dart

@@ -34,14 +34,14 @@ class _PdfViewerScreenState extends State<PdfViewerScreen> {
   void _zoomIn() {
     setState(() {
       _zoomLevel = (_zoomLevel * 1.3).clamp(0.8, 5.0);
-      _transformationController.value = Matrix4.identity()..scale(_zoomLevel);
+      _transformationController.value = Matrix4.diagonal3Values(_zoomLevel, _zoomLevel, _zoomLevel);
     });
   }
 
   void _zoomOut() {
     setState(() {
       _zoomLevel = (_zoomLevel / 1.3).clamp(0.8, 5.0);
-      _transformationController.value = Matrix4.identity()..scale(_zoomLevel);
+      _transformationController.value = Matrix4.diagonal3Values(_zoomLevel, _zoomLevel, _zoomLevel);
     });
   }
 
@@ -196,7 +196,7 @@ class _PdfViewerScreenState extends State<PdfViewerScreen> {
                               borderRadius: BorderRadius.circular(4),
                               boxShadow: [
                                 BoxShadow(
-                                  color: Colors.black.withOpacity(0.15),
+                                  color: Colors.black.withValues(alpha: 0.15),
                                   blurRadius: 10,
                                   offset: const Offset(0, 3),
                                 ),
@@ -235,7 +235,7 @@ class _PdfViewerScreenState extends State<PdfViewerScreen> {
               elevation: 4,
               shape: RoundedRectangleBorder(
                   borderRadius: BorderRadius.circular(24)),
-              color: Colors.white.withOpacity(0.92),
+              color: Colors.white.withValues(alpha: 0.92),
               child: Padding(
                 padding: const EdgeInsets.symmetric(vertical: 4, horizontal: 2),
                 child: Column(