feat(sockets): message delivery guarantees + offline queue

[ayo-mide55]

Closes #147

Adds at-least-once delivery guarantees for driver-bound socket messages in src/sockets/messageQueue.ts:

• ACK gating — an ACK-required message is retained until the client acks it (empty object counts as an ack); no ack ⇒ re-delivery on timeout up to a bounded retry budget.
• Bounded queue — per-driver bound (SOCKET_MESSAGE_QUEUE_MAX, default 100) with oldest-first eviction.
• Retry budget — SOCKET_MESSAGE_MAX_RETRIES (default 5) automatic re-deliveries after ACK timeouts; exhausted messages stay queued for the next reconnect flush.
• Idempotent flush on reconnect — flush() re-delivers each unacked message exactly once, so a reconnecting driver never gets duplicates.
• Per-driver isolation and safe disconnect handling.

New env knobs documented in .env.example/src/config/env.ts (validated). socket.service.ts wired to the new callbacks.

Tests: tests/messageQueue.test.ts — 17 pass (queued until ACK, ACK removal, reconnect flush without duplicates, ACK-timeout retry, queue bound/eviction, per-driver isolation).

Run: npx jest tests/messageQueue.test.ts --runInBand --forceExit.

[Tybravo]

@ayo-mide55

Thank you for contributing to the project