fix(plugins): refresh local repositories when preserving them on empty remote

The preserve-local branch previously returned before scheduling any
repository refreshes, leaving local repositories stale for the whole
session on cold start. They now refresh (without pushing) before the
early return, matching the non-empty-remote path.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

composeApp/src/fullCommonMain/kotlin/com/nuvio/app/features/plugins/PluginRepository.kt

@@ -116,6 +116,9 @@ actual object PluginRepository {
 
             if (shouldPreserveLocalPluginRepositories(urls, _uiState.value.repositories)) {
                 log.w { "pullFromServer — remote empty while local has repositories; preserving local" }
+                _uiState.value.repositories.forEach { repo ->
+                    refreshRepository(repo.manifestUrl, pushAfterRefresh = false)
+                }
                 initialized = true
                 return
             }