refactor(cms): deduplicate shared admin components and fix studio batch completion

- fix(studio): stop markBatchDone infinite recursion so batches complete
- refactor(api): merge api-response into api and drop the duplicate module
- refactor(media): extract shared media loader and URL validator
- refactor(ui): extract shared LoadingSpinner for site and admin groups
- refactor(dates): consolidate raw date formatting into formatDate util
- refactor(logs): share a single generic log-list loader across tables
- refactor(theme): merge both ColorField components and reuse contrast helpers
- refactor(import): extract shared ImportErrorBanner and SearchInput
- chore(): remove dead theme-editor-tabs after inlining tab components

src/lib/api.ts

@@ -22,6 +22,11 @@ export function apiJson(data: unknown, init?: ResponseInit): NextResponse {
 	});
 }
 
+/** Standard success envelope: { ok: true, ...data }. */
+export function apiOk(data?: Record<string, unknown>): NextResponse {
+	return apiJson({ ok: true, ...data });
+}
+
 /** Standard error envelope. */
 export function apiError(message: string, status = 400): NextResponse {
 	return apiJson({ error: message }, { status });