fix: no reconnect storm on send failure, reduce refresh to 1 FPS

- try_send: don't reconnect on failure, just skip and retry next cycle
- Background refresh: 5 FPS → 1 FPS to reduce router serial load
- Revert Bridge.run() - RouterBridge uses Zephyr RTOS thread

sketch/sketch.ino

@@ -121,6 +121,5 @@ void setup() {
 }
 
 void loop() {
-  Bridge.run();
-  delay(1);
+  delay(1000);
 }