feat(native): system-wide PTT/deafen via a non-consuming key poll (#2)

PTT and deafen are DOM key handlers in cinny and only fire while the Lotus
window has focus — alt-tab into a fullscreen game and the voice controls
stop working.

New native/hotkeys.rs (Windows): `set_global_hotkeys(bindings)` starts a
thread that samples GetAsyncKeyState for the configured W3C key codes every
~8 ms while a call is joined and emits a `lotus-global-hotkey` DOM event
{id, state, ctrl, alt, meta} on each press/release transition; an empty
list stops it. Deliberately NOT RegisterHotKey / a global-shortcut plugin:
those consume the key system-wide (a bare Space PTT would stop every other
app typing spaces). `global_hotkeys_supported` reports false off Windows,
where the commands are no-ops (Linux X11 could poll XQueryKeymap later;
Wayland has no non-consuming path). HotkeyPoll state is managed
unconditionally in setup. Cargo: Win32_UI_Input_KeyboardAndMouse feature.
Cross-checked against windows 0.61 for x86_64-pc-windows-msvc; Linux
cargo check clean.

Web side: cinny 00584d78 (useCallHotkeys + Settings → Calls toggle).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src-tauri/Cargo.toml

@@ -66,6 +66,7 @@ windows = { version = "0.61", features = [
     "Win32_System_Com_StructuredStorage",  # P5-36 jump list (PROPVARIANT)
     "Win32_System_Power",                  # P5-46 no-sleep
     "Win32_System_WinRT",                  # P5-43 SMTC interop
+    "Win32_UI_Input_KeyboardAndMouse",     # cinny-desktop #2 global PTT/deafen poll
     "Win32_UI_Shell",
     "Win32_UI_Shell_Common",               # P5-36 jump list (IObjectArray/IObjectCollection)
     "Win32_UI_Shell_PropertiesSystem",     # P5-36 jump list (IPropertyStore/PKEY_Title)