fix(celery): resolve environment variable hijacking by Celery CLI

- Rename CELERY_BROKER and CELERY_BACKEND to REDIS_DB_CELERY_BROKER and REDIS_DB_CELERY_BACKEND to avoid Celery CLI prefix matching hijacking
- Build canonical broker and backend URLs and force them into os.environ to prevent override by stray environment variables
- Add logging for Celery app initialization with sanitized connection details
- Update celery_app.py to use pre-built URL variables instead of inline construction
- Add documentation reference to celery-env-bug-report.md explaining the environment variable naming convention
- Prevents Celery CLI's Click framework from intercepting broker/backend configuration through environment variables

api/app/core/config.py

@@ -190,8 +190,10 @@ class Settings:
     LOG_FILE_MAX_SIZE_MB: int = int(os.getenv("LOG_FILE_MAX_SIZE_MB", "10"))  # 10MB
 
     # Celery configuration (internal)
-    CELERY_BROKER: int = int(os.getenv("CELERY_BROKER", "1"))
-    CELERY_BACKEND: int = int(os.getenv("CELERY_BACKEND", "2"))
+    # NOTE: 变量名不以 CELERY_ 开头，避免被 Celery CLI 的前缀匹配机制劫持
+    # 详见 docs/celery-env-bug-report.md
+    REDIS_DB_CELERY_BROKER: int = int(os.getenv("REDIS_DB_CELERY_BROKER", "1"))
+    REDIS_DB_CELERY_BACKEND: int = int(os.getenv("REDIS_DB_CELERY_BACKEND", "2"))
 
     # SMTP Email Configuration
     SMTP_SERVER: str = os.getenv("SMTP_SERVER", "smtp.gmail.com")