feat(api+web): stream topic chat live over server-sent events

GET /v1/topics/:name/stream opens an SSE firehose, polled server-side
every 2s and streamed as `message` events. Forward-only — clients
hit /messages once for backfill, then live from connect-time onward.
Heartbeats every 30s keep the connection through proxies.

Web chat panel reads the stream via fetch + ReadableStream so the
bearer token stays in the Authorization header (EventSource can't
set custom headers, which would force token-in-URL leaks). Auto-
reconnect with exponential backoff. setInterval polling removed.

Vercel maxDuration bumped to 300s on the catch-all API route so
streams aren't cut at the 10s default.

drizzle migrations/meta/ deleted — superseded by the filename-
tracked custom runner in apps/broker/src/migrate.ts (c2cd67a).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/app/api/[...route]/route.ts

@@ -2,6 +2,16 @@ import { handle } from "hono/vercel";
 
 import { appRouter } from "@turbostarter/api";
 
+// Streamable endpoints (e.g. /v1/topics/:name/stream SSE) need to keep
+// the connection open for minutes, not the 10s default. 300s is the
+// Vercel Pro ceiling; on Hobby the platform clamps to 60s and the
+// client auto-reconnects via the SSE retry loop.
+export const maxDuration = 300;
+
+// Force dynamic rendering — streaming responses can't be statically
+// optimized and we don't want Next caching SSE traffic.
+export const dynamic = "force-dynamic";
+
 const handler = handle(appRouter);
 export {
   handler as GET,