fix: survive MissingPluginException on startup, fix crash report URL (#146)

Two fixes:

1. notification_service.dart: initNotifications() now catches
   MissingPluginException (and any other init failure) so the app no
   longer crashes when flutter_local_notifications is unavailable on
   some Android devices.  _initialized tracks success; showNewMailNotification
   skips the plugin call when it never initialised.

2. crash_screen.dart: "Report Issue on Codeberg" no longer puts the full
   report in the URL query string.  Long stack traces exceeded browser
   URL-length limits and caused "create issue failed".  The URL now
   carries only the pre-filled title; the user copies the full report
   via "Copy to Clipboard" and pastes it in the issue body.

Tests added:
- test/unit/notification_service_test.dart: verifies initNotifications()
  completes without throwing when the plugin channel is unavailable.
- test/widget/crash_screen_test.dart: verifies the Codeberg URL contains
  the title but no &body= parameter.

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

lib/core/services/notification_service.dart

@@ -1,26 +1,35 @@
 import 'dart:io';
 
+import 'package:flutter/services.dart';
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
 
 const _kChannelId = 'new_mail';
 const _kChannelName = 'New mail';
 
 final _plugin = FlutterLocalNotificationsPlugin();
+bool _initialized = false;
 
 Future<void> initNotifications() async {
-  const android = AndroidInitializationSettings('@mipmap/ic_launcher');
-  await _plugin.initialize(
-    const InitializationSettings(android: android),
-    onDidReceiveNotificationResponse: (_) {},
-  );
-  await _plugin
-      .resolvePlatformSpecificImplementation<
-          AndroidFlutterLocalNotificationsPlugin>()
-      ?.requestNotificationsPermission();
+  try {
+    const android = AndroidInitializationSettings('@mipmap/ic_launcher');
+    await _plugin.initialize(
+      const InitializationSettings(android: android),
+      onDidReceiveNotificationResponse: (_) {},
+    );
+    await _plugin
+        .resolvePlatformSpecificImplementation<
+            AndroidFlutterLocalNotificationsPlugin>()
+        ?.requestNotificationsPermission();
+    _initialized = true;
+  } on MissingPluginException {
+    // Plugin not registered on this device; notifications silently disabled.
+  } catch (_) {
+    // Unexpected initialization failure; notifications silently disabled.
+  }
 }
 
 Future<void> showNewMailNotification(String accountEmail) async {
-  if (!Platform.isAndroid) return;
+  if (!Platform.isAndroid || !_initialized) return;
   await _plugin.show(
     accountEmail.hashCode & 0x7FFFFFFF,
     'New mail',

lib/ui/screens/crash_screen.dart

@@ -112,13 +112,15 @@ class CrashScreen extends StatelessWidget {
                 const SizedBox(height: 16),
                 OutlinedButton.icon(
                   onPressed: () async {
-                    final report = await _buildReport();
+                    // URL carries only the title to avoid exceeding browser
+                    // URL-length limits — long stack traces caused "create
+                    // issue failed" (#146).  Use "Copy to Clipboard" first to
+                    // get the full report, then paste it in the issue body.
                     final title = Uri.encodeComponent(
                       'Crash: ${exception.toString().split('\n').first}',
                     );
-                    final body = Uri.encodeComponent(report);
                     final url = Uri.parse(
-                      'https://codeberg.org/guettli/sharedinbox/issues/new?title=$title&body=$body',
+                      'https://codeberg.org/guettli/sharedinbox/issues/new?title=$title',
                     );
                     try {
                       final launched = await launchUrl(

test/unit/notification_service_test.dart

@@ -0,0 +1,26 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:sharedinbox/core/services/notification_service.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  // Regression test for https://codeberg.org/guettli/sharedinbox/issues/146:
+  // On some Android devices the flutter_local_notifications plugin channel is
+  // absent at startup, throwing MissingPluginException (or a similar error).
+  // initNotifications() must absorb the failure and let the app continue.
+  test(
+      'initNotifications completes without throwing when plugin is unavailable',
+      () async {
+    // In the unit-test environment the native plugin is not registered, so
+    // _plugin.initialize() throws. The fix catches it and keeps _initialized
+    // false.  This test fails before the fix (exception propagates) and passes
+    // after it (exception is swallowed).
+    await expectLater(initNotifications(), completes);
+  });
+
+  test('showNewMailNotification completes without throwing', () async {
+    // Platform.isAndroid is false in tests, so this returns early without
+    // touching the plugin.  Ensures the guard path is exercised.
+    await expectLater(showNewMailNotification('test@example.com'), completes);
+  });
+}

test/widget/crash_screen_test.dart

@@ -59,6 +59,10 @@ void main() {
     await tester.tap(find.text('Report Issue on Codeberg'));
     await tester.pumpAndSettle();
 
+    // Regression for #146: URL must contain only the title, NOT the full
+    // report body.  Long stack traces caused "create issue failed" by
+    // exceeding browser URL-length limits.  The report is copied to clipboard
+    // so the user can paste it into the issue body.
     expect(
       mock.launchedUrl,
       contains('https://codeberg.org/guettli/sharedinbox/issues/new'),
@@ -67,8 +71,9 @@ void main() {
       mock.launchedUrl,
       contains('title=Crash%3A%20TestException%3A%20something%20broke'),
     );
-    expect(mock.launchedUrl, contains('App%20Version%3A%201.0.0%2B42'));
-    expect(mock.launchedUrl, contains('TestException%3A%20something%20broke'));
+    expect(mock.launchedUrl, isNot(contains('&body=')));
+    expect(mock.launchedUrl, isNot(contains('App%20Version')));
+    expect(mock.launchedUrl, isNot(contains('Stack%20Trace')));
   });
 
   testWidgets(