rpc-proxy worker
- POST /rpc        -> JSON-RPC (HTTP) with adaptive fallback & batching
- WS   /rpc        -> WebSocket proxy (Chainstack /ws handled)
- GET  /rpc/health -> health check
- *    /x/pump/*   -> proxy to PUMP_BASE
- *    /jup/*      -> proxy to Jupiter (lite/api/v6) with key & fallback + own rate limiter
- GET  /__metrics  -> in-memory metrics