various small fixes

- clean up webproxy getExtUrl
- bugfix init multicast on wifi reconnect
- add ip address of remote AP that's taken over a tag
- renamed button 'edit contentFS' to 'file system'

ESP32_AP-Flasher/src/main.cpp

@@ -140,7 +140,6 @@ void setup() {
     updateBrightnessFromConfig();
 
     init_web();
-    init_udp();
 
 #ifdef HAS_RGB_LED
     rgbIdle();