Fix/linux nonlatin keyboard layout

[TheCyberAngel]

This fixes keyboard bindings on Linux when using non-Latin keyboard layouts such as Ukrainian or Russian.

Previously SDL key events were mapped through layout-dependent keycodes. On non-Latin layouts, keys like WASD could resolve to unmapped Unicode keycodes and become Keys.None, causing movement and default keybindings to break.

The fix adds a scancode-based fallback:

• KeyDown/KeyUp now fall back to physical SDL scancodes if keycode mapping fails
• QwertyToCurrentLayout also falls back to scancodes, preventing reset-to-default bindings from becoming Keys.None

Text input remains layout-aware, so chat and text fields still support non-English input correctly.

Tested on Linux with Ukrainian and Russian keyboard layout:

• gameplay movement works
• rebinding keys works
• resetting controls no longer produces Keys.None
• chat input still supports Kyrylic text