chore: 移除全局 API 与 WS 限流并修复代理配置

移除 fastapi-limiter 依赖及相关限流逻辑，更新健康检查请求头并信任反向代理转发头，避免生产环境 HTTPS 误判导致 301 循环。

backend/app/api/v1/routers.py

@@ -1,8 +1,7 @@
 """v1 路由总表"""
 
-from fastapi import APIRouter, Depends
+from fastapi import APIRouter
 
-from app.core.rate_limiter import api_rate_limiter
 from app.modules.ai.chat.controller import ChatRouter
 from app.modules.common.file.controller import FileRouter
 from app.modules.generator.gencode.controller import GenRouter
@@ -64,7 +63,7 @@ DOMAIN_CONTROLLERS: dict[str, list[APIRouter]] = {
     "/common": [FileRouter],
 }
 
-api_v1 = APIRouter(dependencies=[Depends(api_rate_limiter)])
+api_v1 = APIRouter()
 for prefix, controllers in DOMAIN_CONTROLLERS.items():
     router = APIRouter(prefix=prefix)
     for controller in controllers: