feat: microservices scaffold + Auth Service (Step 1)

- Add shared/ module: config, db, models, schemas, redis utilities
- Add Auth Service (services/auth/): register, login, refresh, me,
  ForwardAuth /verify endpoint for Traefik
- Add Traefik config: ACME/Cloudflare DNS-01, dynamic routing,
  ForwardAuth middleware, sticky sessions for WS Gateway
- Add service scaffolds: ws-gateway, chat, batch-agent, billing (READMEs)
- Add redis>=5.0.0 to requirements.txt
- Monolith app/ is untouched — strangler fig migration

services/auth/requirements.txt

@@ -0,0 +1,11 @@
+fastapi>=0.115.0
+uvicorn[standard]>=0.34.0
+gunicorn>=22.0.0
+pydantic>=2.10.0
+pydantic-settings>=2.7.0
+python-jose[cryptography]>=3.3.0
+sqlalchemy>=2.0.0
+asyncpg>=0.30.0
+bcrypt>=4.2.0
+cryptography>=42.0.0
+python-dotenv>=1.0.0