Fix keyboard and mouse HID mapping for extended keys and buttons

[JerryJohnsonLee]

Summary

• Fix incorrect USB HID codes for Page Up, Page Down, and End keys that made them non-functional
• Fix F11/F12 mapping (Linux codes 87/88 were incorrectly assumed to be sequential with F1-F10)
• Add full numpad support (NumLock, KP0-KP9, KP Enter, KP +/-/*/.)
• Add missing keys: PrintScreen, ScrollLock, Pause, Menu/Application
• Add mouse side button support (5 buttons instead of 3) with BTN_FORWARD/BTN_BACK aliases
• Add horizontal scroll wheel support (REL_HWHEEL / AC Pan) for mice like the Logitech MX Master 3S
• Update mouse HID descriptor and report format from 4 to 5 bytes
• Fix incorrect Linux input event code constants to match input-event-codes.h

Problem

Several key categories and mouse features were broken in the Bluetooth-to-USB relay:

Keyboard:

• Page Up/Down produced Up/Down Arrow instead (both mapped to the same HID codes 0x52/0x51)
• End key produced Page Up (mapped to HID 0x4B instead of 0x4D)
• F11/F12 were unmapped — the F-key loop mapped Linux codes 59-70 sequentially, but F11=87 and F12=88 in Linux (codes 69/70 are NumLock/ScrollLock)
• Numpad keys had no mappings at all

Mouse:

• HID descriptor only declared 3 buttons (left/middle/right), so side button bits were silently ignored by the host OS
• No horizontal scroll axis in the descriptor, making mice such as the MX Master 3S thumb wheel non-functional

Changes

internal/relay/keyboard.go

• Fix navigation cluster HID codes: Page Up → 0x4B, End → 0x4D, Page Down → 0x4E
• Fix F-key loop to only cover F1-F10 (codes 59-68), add explicit F11 (87→0x44) and F12 (88→0x45)
• Add 17 numpad key mappings (NumLock, KP0-9, KP operators)
• Add PrintScreen (0x46), ScrollLock (0x47), Pause (0x48), Menu (0x65)
• Fix all KEY_* constants to match Linux input-event-codes.h

internal/relay/mouse.go

• Expand report from [4]byte to [5]byte (new byte 4 = horizontal wheel)
• Add case 6 (REL_HWHEEL) handler for horizontal scroll
• Extend button range from 272-276 to 272-278, mapping BTN_FORWARD(277)→bit 4 and BTN_BACK(278)→bit 3
• Update validateEvent to accept the extended button range

scripts/setup_gadgets.sh

• Update mouse report_length from 4 to 5
• Replace mouse HID descriptor: 5 buttons (was 3), X/Y, vertical wheel, horizontal wheel (AC Pan via Consumer usage page 0x0C)

internal/relay/keyboard_test.go

• Add test cases for F1, F11, F12, Home, End, Page Up, Page Down, Up Arrow, NumLock, KP5, KP Enter, and unmapped key handling

internal/relay/mouse_test.go

• Update all existing test expected reports from 4 to 5 bytes
• Add tests for horizontal scroll (REL_HWHEEL), side buttons (BTN_SIDE, BTN_EXTRA), and aliased buttons (BTN_FORWARD, BTN_BACK)
• Add validation tests for extended button range and horizontal wheel events