Bug Fix: Add debouncing to GUI navigation to prevent LVGL memory fragmentation

[Stuckya]

I was encountering intermittent crashes when my kids were using the remote. This led me to debugging the crashes and I uncovered 3 issues along the way. This was the 3rd issue.

Problem:

LVGL memory fragmentation crashes during rapid GUI navigation, causing heap corruption in remove_free_block and lv_style_set_prop_internal.

Root Cause:

• Rapid button pressing of GUI navigation keys (ex: KEY_RIGHT → scene_gui_next()) caused excessive LVGL object creation/deletion cycles.
• Memory allocator (TLSF) became fragmented under stress, leading to invalid memory access.

Proposed Fix:

1. Added 100ms of debouncing to GUI navigation commands (scene_gui_next, scene_gui_prev).
2. Created isGuiNavigationDebounced() helper function to improve readability and encapsulate logic which prevents rapid scene changes.
3. Overall, this fix reduces stress on LVGL memory allocator during fast button pressing that would otherwise result in rapid scene changes.