feat: add gateway API, voice service, WebSocket hub, and startup entry

- services/gateway/api: net/http router with JWT auth, stub login, 6 tests
- services/gateway/ws: WebSocket hub with echo support
- services/voice: STT/TTS provider chain with fallback, 6 tests
- cmd/cyrene/main.go: single binary startup, 108 tests total
- Smoke test: health check + login verified on :8080

backend/go.mod

@@ -9,3 +9,5 @@ require (
 	github.com/lib/pq v1.12.3
 	golang.org/x/crypto v0.54.0
 )
+
+require github.com/gorilla/websocket v1.5.3