feat(api): add Redis-backed query cache persistence layer

Add tRPC router (queryCache.getItem/setItem/removeItem) for persisting
TanStack Query cache entries to Redis, scoped per user and board.
Includes isPersistableWidgetQueryKey filter that excludes widget.app.ping,
and comprehensive tests covering access control, TTL expiry, and size limits.

packages/api/src/root.ts

@@ -24,6 +24,7 @@ export const appRouter = createTRPCRouter({
   cronJobs: lazy(() => import("./router/cron-jobs").then((mod) => mod.cronJobsRouter)),
   apiKeys: lazy(() => import("./router/apiKeys").then((mod) => mod.apiKeysRouter)),
   media: lazy(() => import("./router/medias/media-router").then((mod) => mod.mediaRouter)),
+  queryCache: lazy(() => import("./router/query-cache").then((mod) => mod.queryCacheRouter)),
   updateChecker: lazy(() => import("./router/update-checker").then((mod) => mod.updateCheckerRouter)),
   certificates: lazy(() => import("./router/certificates/certificate-router").then((mod) => mod.certificateRouter)),
   bangs: lazy(() => import("./router/bangs/bangs-router").then((mod) => mod.bangsRouter)),