Add system tray icon, file logging, and fix Windows hotkey conflict

- Adds fyne.io/systray with a programmatic monkey face icon and Quit menu item
- Logs to discord-lobby-mute.log next to the exe so startup errors are visible
  without a console window
- Windows now uses raw Win32 RegisterHotKey in a locked goroutine instead of
  golang.design/x/hotkey, avoiding a deadlock where systray and the hotkey
  library both try to own the main thread message loop
- Build with: GOOS=windows GOARCH=amd64 go build -ldflags "-H windowsgui" -o discord-lobby-mute.exe .

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

keybind_windows.go

@@ -2,7 +2,14 @@
 
 package main
 
-import "golang.design/x/hotkey"
+import (
+	"fmt"
+	"runtime"
+	"syscall"
+	"unsafe"
+
+	"golang.design/x/hotkey"
+)
 
 var modMap = map[string]hotkey.Modifier{
 	"ctrl":  hotkey.ModCtrl,
@@ -11,3 +18,71 @@ var modMap = map[string]hotkey.Modifier{
 	"win":   hotkey.ModWin,
 	"super": hotkey.ModWin,
 }
+
+var (
+	user32             = syscall.NewLazyDLL("user32.dll")
+	procRegisterHotKey = user32.NewProc("RegisterHotKey")
+	procGetMessageW    = user32.NewProc("GetMessageW")
+)
+
+// winMsg mirrors the Win32 MSG struct.
+type winMsg struct {
+	hwnd    uintptr
+	message uint32
+	wParam  uintptr
+	lParam  uintptr
+	time    uint32
+	ptX     int32
+	ptY     int32
+}
+
+func startHotkey(keybind string) (<-chan struct{}, error) {
+	mods, key, err := parseKeybind(keybind)
+	if err != nil {
+		return nil, err
+	}
+
+	// hotkey.Modifier and hotkey.Key values on Windows are the native Win32
+	// MOD_* and VK_* constants, so they can be passed directly to RegisterHotKey.
+	var modFlags uintptr
+	for _, m := range mods {
+		modFlags |= uintptr(m)
+	}
+	vk := uintptr(key)
+
+	ch := make(chan struct{}, 1)
+	ready := make(chan error, 1)
+
+	go func() {
+		runtime.LockOSThread()
+		// Intentionally no defer UnlockOSThread — this goroutine owns its OS
+		// thread for the lifetime of the app to keep the hotkey message queue alive.
+
+		ret, _, e := procRegisterHotKey.Call(0, 1, modFlags, vk)
+		if ret == 0 {
+			ready <- fmt.Errorf("RegisterHotKey: %w", e)
+			return
+		}
+		close(ready)
+
+		const wmHotkey = 0x0312
+		var msg winMsg
+		for {
+			r, _, _ := procGetMessageW.Call(
+				uintptr(unsafe.Pointer(&msg)), 0, wmHotkey, wmHotkey,
+			)
+			if r == 0 || r == ^uintptr(0) { // WM_QUIT or error
+				return
+			}
+			select {
+			case ch <- struct{}{}:
+			default:
+			}
+		}
+	}()
+
+	if err := <-ready; err != nil {
+		return nil, err
+	}
+	return ch, nil
+}