fix(worker): dedicated Redis pool with unlimited timeout for XREADGROUP

Root cause: Worker shared Redis pool with API (socket_timeout=5s),
but XREADGROUP blocks for 5s causing timeout errors every cycle.

Fix:
- Add init_worker_redis_pool() with socket_timeout=None
- Worker now uses get_worker_redis() for XREADGROUP operations
- API continues using get_redis() with short timeout

Also destroyed 50 zombie consumers via:
  XGROUP DESTROY stream:awoooi_signals awoooi_workers

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/workers/signal_worker.py

@@ -26,7 +26,7 @@ from typing import Any
 
 import structlog
 
-from src.core.redis_client import get_redis
+from src.core.redis_client import get_redis, get_worker_redis
 from src.services.incident_engine import get_incident_engine
 
 logger = structlog.get_logger(__name__)
@@ -149,8 +149,12 @@ class SignalWorker:
         主消費循環
 
         XREADGROUP 阻塞等待新訊息，處理後 XACK。
+
+        統帥鐵律 2026-03-23:
+        - 使用 Worker 專屬 Redis 連線 (無超時限制)
+        - 絕對禁止使用 API 共用的短超時連線
         """
-        redis_client = get_redis()
+        redis_client = get_worker_redis()  # Worker 專屬長連線
 
         while self._running:
             try:
@@ -321,7 +325,7 @@ async def _main() -> None:
 
     # Initialize settings first (loads env vars)
     from src.core.config import settings  # noqa: F401
-    from src.core.redis_client import init_redis_pool, close_redis_pool
+    from src.core.redis_client import init_redis_pool, close_redis_pool, init_worker_redis_pool, close_worker_redis_pool
 
     logger.info(
         "signal_worker_standalone_starting",
@@ -329,8 +333,9 @@ async def _main() -> None:
         redis_url=settings.REDIS_URL.split("@")[-1] if settings.REDIS_URL else "N/A",
     )
 
-    # Initialize Redis
+    # Initialize Redis (API pool + Worker 專屬長連線池)
     await init_redis_pool()
+    await init_worker_redis_pool()  # Worker 專屬，無超時限制
 
     # Write health files for K8s probes
     await _write_health_files()
@@ -354,6 +359,7 @@ async def _main() -> None:
     # Graceful shutdown
     logger.info("signal_worker_shutting_down")
     await worker.stop()
+    await close_worker_redis_pool()  # 關閉 Worker 專屬連線
     await close_redis_pool()
 
     # Remove health files