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/include/ota.h

@@ -4,7 +4,6 @@
 
 void handleSysinfoRequest(AsyncWebServerRequest* request);
 void handleCheckFile(AsyncWebServerRequest* request);
-void handleGetExtUrl(AsyncWebServerRequest* request);
 void handleLittleFSUpload(AsyncWebServerRequest* request, String filename, size_t index, uint8_t* data, size_t len, bool final);
 void handleUpdateOTA(AsyncWebServerRequest* request);
 void firmwareUpdateTask(void* parameter);