fix: use SuperJSON for cache persistence and add null guards to all widgets

SuperJSON preserves Date/Map/Set types through the Redis cache round-trip,
fixing RangeError crashes from date formatting. Added defensive null/undefined
guards across all widget components to handle useQuery loading states and
potential cache shape mismatches.

packages/widgets/src/media-transcoding/panels/queue.panel.tsx

@@ -27,7 +27,7 @@ export function QueuePanel(props: QueuePanelProps) {
 
   const t = useI18n("widget.mediaTranscoding.panel.queue");
 
-  if (queue.array.length === 0) {
+  if ((queue.array ?? []).length === 0) {
     return (
       <Center style={{ flex: "1" }}>
         <Title order={6}>{t("empty")}</Title>
@@ -53,7 +53,7 @@ export function QueuePanel(props: QueuePanelProps) {
           </TableTr>
         </TableThead>
         <TableTbody>
-          {queue.array.map((item) => (
+          {(queue.array ?? []).map((item) => (
             <TableTr key={item.id}>
               <TableTd py={2}>
                 <Group gap={4} wrap="nowrap">

packages/widgets/src/media-transcoding/panels/workers.panel.tsx

@@ -26,7 +26,7 @@ interface WorkersPanelProps {
 export function WorkersPanel(props: WorkersPanelProps) {
   const t = useI18n("widget.mediaTranscoding.panel.workers");
 
-  if (props.workers.length === 0) {
+  if ((props.workers ?? []).length === 0) {
     return (
       <Center style={{ flex: "1" }}>
         <Title order={6}>{t("empty")}</Title>