fix(chat): resolve Auto-route failover event-loop freeze (#812)

Root cause: ensure_structured_column() executed a synchronous blocking
engine.connect().execute(SELECT information_schema.columns ...) inside the
async request path (_build_chat_history / _maybe_compress_history), freezing
the uvicorn event loop and hanging all endpoints (~200s, recovered only by
docker restart).

Fix:
- chat_context.py: remove per-request ensure_structured_column() calls; run
  once idempotently at app startup (main.py lifespan). Use CURRENT_DATABASE()
  for PostgreSQL compatibility.
- main.py: add startup-only ensure_structured_column() hook (try/except).
- llm_client.py: trust_env=False + bounded httpx.Timeout/wait_for so broken
  endpoints fail fast instead of hanging the event loop.
- chat_service.py: run media generation in a background daemon thread with its
  own event loop (_launch_media_task_bg) so SSE end does not cancel image/video
  tasks (#811); remove TEMP faulthandler diagnostic.

Safe-align: persist accumulated live container changes (admin/*, knowledge,
market, models, config, observability, mcp_client, platform_knowledge,
im_bot_platform, chat_media, capability_registry, requirements) and add
workflow_templates.

Verified: live failover test (model-006 -> conn-refused) returns in ~1.9s with
concurrent login 0.83s/200; event-loop responsiveness restored (sub-second).

backend/python/app/api/admin/privacy_admin.py

@@ -442,7 +442,7 @@ def revoke_license(
         raise HTTPException(404, "License not found")
 
     _execute_raw(db, text(
-        "UPDATE offline_licenses SET status = 'revoked', revoked_reason = :reason, is_active = 0 WHERE id = :lid"
+        "UPDATE offline_licenses SET status = 'revoked', revoked_reason = :reason, is_active = false WHERE id = :lid"
     ), {"reason": reason, "lid": license_id})
 
     return {"code": 0, "message": "License revoked"}
@@ -623,7 +623,7 @@ def get_usage_stats(db: Session = Depends(get_db)):
         "SELECT COUNT(DISTINCT user_hash) FROM usage_reports"
     ))
     today_reports = _execute_raw(db, text(
-        "SELECT COUNT(*) FROM usage_reports WHERE DATE(created_at) = CURDATE()"
+        "SELECT COUNT(*) FROM usage_reports WHERE DATE(created_at) = CURRENT_DATE"
     ))
     by_type = _execute_raw(db, text(
         "SELECT report_type, COUNT(*) as cnt FROM usage_reports GROUP BY report_type"