Metrics registration can panic at startup

[qj0r9j0vc2]

Problem

RPC metrics in crates/rpc/src/metrics.rs use expect() during lazy static initialization, which will panic if metric registration fails.

Details

static ref RPC_REQUESTS_TOTAL: IntCounterVec = IntCounterVec::new(...)
    .expect("Failed to register rpc_requests_total metric")

All metric registrations follow this pattern:

• RPC_REQUESTS_TOTAL
• RPC_REQUEST_DURATION
• RPC_ACTIVE_CONNECTIONS
• RPC_WS_SUBSCRIPTIONS
• RPC_RATE_LIMIT_REJECTIONS

Impact

• If Prometheus registry has naming conflicts or is exhausted, node crashes at startup
• No graceful degradation to running without metrics