[BUG] Docker Gateway port 18789 not exposed in docker-compose.yml

## Bug: Gateway Port Not Exposed in Docker

**File:** `docker-compose.yml` lines 5-8

**Issue:** Gateway port 18789 not exposed in Docker compose, making container networking fail.

**Impact:** Users cannot connect to PilotDeck Gateway from outside the container.

**Recommended Fix:** Add to docker-compose.yml:
```yaml
ports:
  - "18789:18789"
```
