feat: add Deezer entry in provider priority UI and improve release changelog

- Add 'deezer' case with icon to _ProviderItem in provider_priority_page.dart
- Fix release.yml: deterministic previous-tag lookup for Full Changelog link
- Strip version header line and author attribution from Telegram changelog
- cliff.toml: hide repo owner username from commit attribution
- cliff.toml: remove PR number stripping preprocessor

lib/screens/settings/provider_priority_page.dart

@@ -334,6 +334,12 @@ class _ProviderItem extends StatelessWidget {
         );
       case 'qobuz':
         return _ProviderInfo(name: 'Qobuz', icon: Icons.album, isBuiltIn: true);
+      case 'deezer':
+        return _ProviderInfo(
+          name: 'Deezer',
+          icon: Icons.graphic_eq,
+          isBuiltIn: true,
+        );
       case 'youtube':
         return _ProviderInfo(
           name: 'YouTube',