feat(backend,frontend): migrate data APIs from REST to native tRPC over WebSocket

Replace REST module routers with a single typed tRPC appRouter served over
/trpc (HTTP + WebSocket), and rewire the frontend to call it via
@trpc/client wsLink (browser) and httpLink (RSC data layer). Existing
/api/health + /api/metrics stay as plain Express for infra scraping.

Notable fixes surfaced by the live smoke test:
- Express 5 / path-to-regexp v8 rejects the /trpc/* wildcard route; use a
  prefix middleware that computes opts.path from the URL instead.
- nodeHTTPRequestHandler treats opts.path as the literal procedure path, so
  it is derived per-request from req.url.
- Two ws servers on one http.Server (the /ws voice socket + /trpc) collided
  and returned 400 on upgrade; both now use noServer + a manually routed
  server.on('upgrade') keyed by path.

Verified: BE tsc+biome+40 vitest green; FE tsc+biome green; live
HTTP and WebSocket calls returned real prod data.

Co-Authored-By: Claude Opus 4.5 (1M context) <noreply@anthropic.com>

services/frontend/src/lib/api/media.ts

@@ -1,11 +1,12 @@
+import { trpc } from "@/lib/trpc/client";
 import type { MediaState } from "@/lib/types";
-import { api } from "./client";
 
 export const mediaApi = {
-  getStatus: () => api.get<MediaState>("/api/media/status"),
+  getStatus: () => trpc.media.status.query() as unknown as Promise<MediaState>,
   queue: (source: string, mode: string) =>
-    api.post<MediaState>("/api/media/queue", { source, mode }),
-  skip: () => api.post<MediaState>("/api/media/skip", {}),
-  stop: () => api.post<MediaState>("/api/media/stop", {}),
-  loop: (loop: boolean) => api.post<MediaState>("/api/media/loop", { loop }),
+    trpc.media.queue.mutate({ source, mode }) as unknown as Promise<MediaState>,
+  skip: () => trpc.media.skip.mutate() as unknown as Promise<MediaState>,
+  stop: () => trpc.media.stop.mutate() as unknown as Promise<MediaState>,
+  loop: (loop: boolean) =>
+    trpc.media.loop.mutate({ loop }) as unknown as Promise<MediaState>,
 };