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/src/native/mod.rs

@@ -11,6 +11,7 @@ use tauri::{AppHandle, Manager};
 pub mod aumid;
 pub mod chrome;
 pub mod focus_assist;
+pub mod hotkeys;
 pub mod jumplist;
 pub mod network;
 pub mod power;