feat(l10n): add localization support for SourceType enum

- Create new extension `SourceTypeL10n` for SourceType enum
- Add `localizedName` method to return localized name based on AppLocalizations
- Cover all SourceType cases for localization

Author: fulleni

lib/shared/extensions/source_type_l10n.dart

@@ -0,0 +1,32 @@
+import 'package:core/core.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/app_localizations.dart';
+
+/// Adds localization support to the [SourceType] enum.
+extension SourceTypeL10n on SourceType {
+  /// Returns the localized name for the source type.
+  ///
+  /// This requires an [AppLocalizations] instance, which is typically
+  /// retrieved from the build context.
+  String localizedName(AppLocalizations l10n) {
+    switch (this) {
+      case SourceType.newsAgency:
+        return l10n.sourceTypeNewsAgency;
+      case SourceType.localNewsOutlet:
+        return l10n.sourceTypeLocalNewsOutlet;
+      case SourceType.nationalNewsOutlet:
+        return l10n.sourceTypeNationalNewsOutlet;
+      case SourceType.internationalNewsOutlet:
+        return l10n.sourceTypeInternationalNewsOutlet;
+      case SourceType.specializedPublisher:
+        return l10n.sourceTypeSpecializedPublisher;
+      case SourceType.blog:
+        return l10n.sourceTypeBlog;
+      case SourceType.governmentSource:
+        return l10n.sourceTypeGovernmentSource;
+      case SourceType.aggregator:
+        return l10n.sourceTypeAggregator;
+      case SourceType.other:
+        return l10n.sourceTypeOther;
+    }
+  }
+}