feat: KKS P240/P241 蓝牙工牌管理系统初始提交

FastAPI + SQLAlchemy + asyncio TCP 服务器，支持设备管理、实时定位、
告警、考勤打卡、蓝牙记录、指令下发、TTS语音播报等功能。

app/extensions.py

@@ -0,0 +1,22 @@
+"""
+Shared extension instances (rate limiter, etc.) to avoid circular imports.
+"""
+
+from starlette.requests import Request
+from slowapi import Limiter
+
+from app.config import settings
+
+
+def _get_real_client_ip(request: Request) -> str:
+    """Extract real client IP from X-Forwarded-For (behind Cloudflare/nginx) or fallback."""
+    forwarded = request.headers.get("X-Forwarded-For")
+    if forwarded:
+        return forwarded.split(",")[0].strip()
+    cf_ip = request.headers.get("CF-Connecting-IP")
+    if cf_ip:
+        return cf_ip.strip()
+    return request.client.host if request.client else "127.0.0.1"
+
+
+limiter = Limiter(key_func=_get_real_client_ip, default_limits=[settings.RATE_LIMIT_DEFAULT])