Feature/oled btns

add main menu OLED UI and button modules with integration to main

Changes included:

• Added display/ module for OLED UI rendering
• history & adc measurement screen ui pending
• Added buttons/ module with GPIO handling and debounce
• Updated main.c to integrate OLED and button events
• Basic navigation and screen updates using button input
• Battery values and MQ3 and BLE status are only placeholders

Folders added

• display
• buttons

File changed

• main.c