Fix keyboard scancode mapping for GFN input translation

[zortos293]

This PR fixes broken keyboard behavior across layouts by replacing the incorrect USB HID usage ID mappings with Windows Set-1 scancodes required by the GFN input protocol.

src/renderer/src/gfn/inputProtocol.ts:

• Replaced codeMap with correct Windows Set-1/extended scancodes for letters (A–Z), digits, punctuation, navigation, and function keys.
• Added mappings for international physical keys (IntlBackslash, IntlRo, IntlYen) to support non-US layouts.
• Consolidated synthetic text injection (mapTextCharToKeySpec) and keyboard event mapping (mapKeyboardEvent) to use the shared codeMap, ensuring consistent scancodes for pasted text and physical presses.
• Fixed numpad (e.g., NumLock, Numpad0) and modifier (e.g., ShiftLeft/Right) scancodes to match Windows scan code set 1.

src/renderer/src/gfn/webrtcClient.ts:

• Updated AFK pulse (sendAntiAfkPulse), paste shortcuts (sendPasteShortcut), and shift handling in sendText to reference the shared codeMap instead of hardcoded values.

Tests & Tooling:

• Added src/renderer/src/gfn/inputProtocol.test.ts with coverage for representative keys (KeyN, KeyT, KeyZ, Escape, IntlBackslash, numpad) and verifying code-over-key precedence.
• Added tsx dependency to devDependencies and created npm run test script.