Issue: Add Pull-Up Resistors for Multiplexer and Button Inputs

### Description
The switch and button inputs connected through the multiplexer currently require proper pull-up configuration to ensure stable and defined signal levels.

This issue focuses on adding pull-up resistors to all relevant input lines.

### Tasks
- Add pull-up resistors for all multiplexer switch inputs
- Add pull-ups for direct button input pins
- Verify compatibility with ATmega32U4 internal pull-ups if applicable
- Update schematic accordingly
- Confirm stable input readings during testing

### Goal
Ensure reliable and noise-resistant input detection for all switches and buttons.

Inspect the project schematic and the wiring for the multiplexer switch inputs and direct button input pins. Check whether the ATmega32U4 internal pull-ups are compatible, update the schematic as needed, and verify stable input readings during hardware testing.

Written by the indexing model from the issue text.