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

shared/redis.py

@@ -0,0 +1,53 @@
+"""Redis client and pub/sub utilities for inter-service communication.
+
+All services that need Redis import from here.
+"""
+
+from __future__ import annotations
+
+import redis.asyncio as aioredis
+
+from shared.config import settings
+
+redis_client: aioredis.Redis = aioredis.from_url(
+    settings.REDIS_URL,
+    decode_responses=True,
+)
+
+
+# ── Channel naming conventions ────────────────────────────────────────
+# See /memories/repo/microservices-architecture.md for full list.
+
+def ws_out_channel(user_id: str) -> str:
+    """Frames to forward to Electron via WS Gateway."""
+    return f"ws:out:{user_id}"
+
+
+def chat_request_channel(user_id: str) -> str:
+    """Chat requests (home + floating) from WS Gateway → Chat Service."""
+    return f"chat:request:{user_id}"
+
+
+def batch_request_channel(user_id: str) -> str:
+    """Batch requests (journey + triggers) from WS Gateway → Batch Agent."""
+    return f"batch:request:{user_id}"
+
+
+def tool_result_key(call_id: str) -> str:
+    """Tool result list: LPUSH by WS Gateway, BRPOP by Chat/Batch."""
+    return f"tool:result:{call_id}"
+
+
+def device_key(user_id: str) -> str:
+    """Device registry hash."""
+    return f"ws:devices:{user_id}"
+
+
+def tier_changed_channel(user_id: str) -> str:
+    """Billing tier change notifications."""
+    return f"tier:changed:{user_id}"
+
+
+def journey_session_key(user_id: str) -> str:
+    """Journey builder session (String + TTL 1800s)."""
+    return f"journey:{user_id}"