LCD remote control to WebSockets + improved mobile button UX (#331)

* Add WebSocket LCD streaming and remote button control

* Add minimum 300ms button press duration and instant LCD feedback. Add immediate LCD image update on button press for instant visual feedback

* Load the image via websockets

* Add PIN-protected LCD button lock with session persistence and improved UX

* Add WebSocket reconnection improvements and visibility-based pause handling

* Improve WebSocket reconnection logic with faster initial retry and immediate reconnect helper

* Remove obsolete websocket_lcd_test.html and move LCD password state to global scope

* Adjust LCD password input width from 6em to 5em

Author: kozmoz