feat: show git commit link on crash screen (#150)

Add the git commit hash to the crash screen as a clickable link to the
Codeberg commit page (using GIT_HASH from --dart-define, same as the
about screen). When the report is copied to clipboard, include it as a
Markdown link so it appears in filed issues.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/screens/crash_screen.dart

@@ -15,6 +15,8 @@ class CrashScreen extends StatelessWidget {
   final Object exception;
   final StackTrace? stackTrace;
 
+  static const _gitHash = String.fromEnvironment('GIT_HASH');
+
   Future<String> _buildReport() async {
     String version = 'unknown';
     try {
@@ -23,7 +25,11 @@ class CrashScreen extends StatelessWidget {
     } catch (_) {}
     final platform =
         '${Platform.operatingSystem} ${Platform.operatingSystemVersion}';
+    final gitLine = _gitHash.isNotEmpty
+        ? 'Git Commit: [$_gitHash](https://codeberg.org/guettli/sharedinbox/commit/$_gitHash)\n'
+        : '';
     return 'App Version: $version\n'
+        '$gitLine'
         'Platform: $platform\n\n'
         'Error:\n```\n$exception\n```\n\n'
         'Stack Trace:\n```\n$stackTrace\n```';
@@ -92,6 +98,32 @@ class CrashScreen extends StatelessWidget {
                     ),
                   ),
                 ],
+                if (_gitHash.isNotEmpty) ...[
+                  const SizedBox(height: 16),
+                  const Text(
+                    'Git Commit:',
+                    style: TextStyle(fontWeight: FontWeight.bold),
+                  ),
+                  const SizedBox(height: 4),
+                  GestureDetector(
+                    onTap: () async {
+                      final url = Uri.parse(
+                        'https://codeberg.org/guettli/sharedinbox/commit/$_gitHash',
+                      );
+                      await launchUrl(
+                        url,
+                        mode: LaunchMode.externalApplication,
+                      );
+                    },
+                    child: const Text(
+                      _gitHash,
+                      style: TextStyle(
+                        color: Colors.blue,
+                        decoration: TextDecoration.underline,
+                      ),
+                    ),
+                  ),
+                ],
                 const SizedBox(height: 24),
                 FilledButton.icon(
                   onPressed: () async {

test/widget/crash_screen_test.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:mockito/mockito.dart';
 import 'package:package_info_plus/package_info_plus.dart';
@@ -76,6 +77,52 @@ void main() {
     expect(mock.launchedUrl, isNot(contains('Stack%20Trace')));
   });
 
+  testWidgets(
+    'CrashScreen copy-to-clipboard includes version and platform info',
+    (tester) async {
+      tester.view.physicalSize = const Size(800, 1200);
+      tester.view.devicePixelRatio = 1.0;
+      addTearDown(() => tester.view.resetPhysicalSize());
+
+      String? clipboardText;
+      tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+        SystemChannels.platform,
+        (MethodCall call) async {
+          if (call.method == 'Clipboard.setData') {
+            clipboardText =
+                (call.arguments as Map<dynamic, dynamic>)['text'] as String?;
+          }
+          return null;
+        },
+      );
+      addTearDown(
+        () => tester.binding.defaultBinaryMessenger
+            .setMockMethodCallHandler(SystemChannels.platform, null),
+      );
+
+      const exception = 'TestException: clipboard test';
+      final stackTrace = StackTrace.current;
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: CrashScreen(exception: exception, stackTrace: stackTrace),
+        ),
+      );
+
+      await tester.tap(find.text('Copy to Clipboard'));
+      await tester.pump();
+      await tester.pump();
+      await tester.pumpAndSettle();
+
+      expect(clipboardText, isNotNull);
+      expect(clipboardText, contains('App Version: 1.0.0+42'));
+      expect(clipboardText, contains('Platform:'));
+      expect(clipboardText, contains('TestException: clipboard test'));
+      // GIT_HASH is empty in test builds — no Git Commit line expected
+      expect(clipboardText, isNot(contains('Git Commit:')));
+    },
+  );
+
   testWidgets(
     'CrashScreen used as root widget — buttons work without ScaffoldMessenger crash',
     (tester) async {