feat: detect LAN client via /api/client-ip for smart sidebar links

dashboard/backend/main.py

@@ -114,6 +114,10 @@ async def startup_event():
 async def health():
     return {"status": "ok"}
 
+@app.get("/api/client-ip")
+async def client_ip(request: Request):
+    return {"ip": request.client.host}
+
 # Public auth endpoints
 app.include_router(auth.router, prefix="/api/auth", tags=["auth"])