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>
