feat: add QR code generation support and rate limiting for known device probes

src/config/limits.ts

@@ -35,6 +35,9 @@
     // /api/sync read request budget per minute.
     // /api/sync 读请求每分钟配额。
     syncReadRequestsPerMinute: 1000,
+    // /api/devices/knowndevice probe budget per IP per minute.
+    // /api/devices/knowndevice 每 IP 每分钟探测配额。
+    knownDeviceRequestsPerMinute: 10,
     // Fixed window size for API rate limiting in seconds.
     // API 限流固定窗口大小（秒）。
     apiWindowSeconds: 60,