refactor: 统一 Redis 连接管理，改用 RedisService

- App 启动时初始化 RedisService，关闭时释放连接
- Celery worker 通过 worker_process_init 钩子初始化 Redis
- Agent 端点改用 RedisService 替代直接创建连接
- Celery task 改为 async def，使用统一连接
- 删除无用的 infra 模块和 core/http/models
- 日志脱敏，不记录 Redis 密码
- 初始化失败时 fail-fast
- 异常发布添加二级保护

backend/src/app.py

@@ -1,18 +1,26 @@
 from __future__ import annotations
 
+from contextlib import asynccontextmanager
+from typing import AsyncGenerator
+
 from fastapi import FastAPI, HTTPException, Request
 from fastapi.exceptions import RequestValidationError
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse
+from pydantic import BaseModel
 from starlette.exceptions import HTTPException as StarletteHTTPException
 
 from core.config.settings import config
-from core.http.models import HealthResponse
 from core.http.response import build_problem_details
 from core.logging import configure_logging, get_logger, log_service_banner
+from services.base.redis import redis_service
 from v1.router import router as mobile_router
 
 
+class HealthResponse(BaseModel):
+    status: str
+
+
 configure_logging(config)
 
 log_service_banner(
@@ -20,7 +28,26 @@ log_service_banner(
     environment=config.runtime.environment,
 )
 
-app = FastAPI()
+logger = get_logger("api.app")
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
+    initialized = await redis_service.initialize()
+    if not initialized:
+        logger.error("Redis service failed to initialize, aborting startup")
+        raise RuntimeError("Redis service initialization failed")
+    logger.info(
+        "Redis service initialized",
+        host=config.redis.host,
+        db=config.redis.db,
+    )
+    yield
+    await redis_service.close()
+    logger.info("Redis service closed")
+
+
+app = FastAPI(lifespan=lifespan)
 app.add_middleware(
     CORSMiddleware,
     allow_origins=config.cors.allow_origins,
@@ -29,7 +56,6 @@ app.add_middleware(
     allow_headers=config.cors.allow_headers,
 )
 app.include_router(mobile_router)
-logger = get_logger("api.app")
 
 logger.info(
     "Web application initialized",