Add priority WiFi failover

docs/UART_PROTOCOL.md

@@ -190,3 +190,18 @@ Pico sends:
     {"type":"wifi_clear"}
 
 AP mode remains enabled as the recovery path.
+
+## WiFi Priority
+
+WiFi configuration supports multiple saved networks.
+
+Lower priority numbers are tried first.
+
+Example:
+
+    {"type":"config_wifi","networks":[{"ssid":"Starlink","password":"password","priority":1},{"ssid":"Home WiFi","password":"password","priority":2}]}
+
+Runtime behavior:
+
+    If STA disconnects, the ESP32 retries saved networks by priority every 30 seconds.
+    AP mode remains available as a recovery path.