refactor: remove author field from extension manifest and UI

lib/screens/settings/extension_detail_page.dart

@@ -50,7 +50,6 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
         name: '',
         displayName: 'Unknown',
         version: '0.0.0',
-        author: 'Unknown',
         description: '',
         enabled: false,
         status: 'error',
@@ -206,10 +205,6 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
                         ),
                       ],
                       const SizedBox(height: 16),
-                      _InfoRow(
-                        label: context.l10n.extensionAuthor,
-                        value: extension.author,
-                      ),
                       _InfoRow(
                         label: context.l10n.extensionId,
                         value: extension.id,

lib/screens/settings/extensions_page.dart

@@ -425,7 +425,7 @@ class _ExtensionItem extends StatelessWidget {
                         hasError
                             ? extension.errorMessage ??
                                   context.l10n.extensionsErrorLoading
-                            : 'v${extension.version} ${context.l10n.extensionsAuthor(extension.author)}',
+                            : 'v${extension.version}',
                         style: Theme.of(context).textTheme.bodySmall?.copyWith(
                           color: hasError
                               ? colorScheme.error