feat(mcpedia): Phase 3 — async indexing (BullMQ), git-sync webhook, revisions, MCP Resources

- packages/queue: ioredis singleton + BullMQ Queue/Worker (prefix mcpedia:
  on shared imrnes Redis :6379); apps/worker runs startWorker()
- @mcpedia/core: indexContentFile/runFullIndex (single indexing entry point
  shared by script/worker/hook) + revision.service (list/get/restore)
- document_revisions table (migration 0002) — snapshots only on body change
- apps/api: POST /hooks/reindex + /hooks/index webhooks; tRPC revisions,
  getRevision, restoreRevision, jobStatus, queueStatus
- apps/mcp: register MCP Resources mcpedia://docs{/,+slug/chunks/revisions}
  ({+slug} RFC6570 reserved expansion for slugs containing /)
- apps/mcp zod pinned to ^4 to match MCP SDK 1.30 compiled types
  (resolves registerTool TS2589/ShapeOutput skew)
- scripts/enqueue.ts one-shot job enqueue helper; indexer refactored to runFullIndex
- PHASES.md/README/.env.example/docs updated

apps/worker/src/index.ts

@@ -0,0 +1,12 @@
+import { startWorker } from "@mcpedia/queue/worker";
+
+// Keep the process alive: the worker listens on the BullMQ queue until a
+// SIGINT/SIGTERM closes it (handled inside startWorker).
+const worker = await startWorker();
+
+// Heartbeat so the supervisor/operator can see liveness without scraping logs.
+const heartbeat = setInterval(() => {
+  console.log(`[worker] alive, ${worker.name} queue="${worker.name}"`);
+}, 30_000);
+
+worker.on("closed", () => clearInterval(heartbeat));