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>

icon.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"bytes"
+	"image"
+	"image/color"
+	"image/png"
+)
+
+func monkeyIcon() []byte {
+	const size = 32
+	img := image.NewRGBA(image.Rect(0, 0, size, size))
+
+	brown := color.RGBA{110, 72, 38, 255}
+	tan   := color.RGBA{210, 175, 130, 255}
+	pink  := color.RGBA{190, 130, 110, 255}
+	dark  := color.RGBA{15, 8, 3, 255}
+	white := color.RGBA{255, 255, 255, 255}
+
+	// Ears drawn first so the head circle overlaps the inner edge naturally.
+	fillCircle(img, 4, 13, 5, brown)
+	fillCircle(img, 28, 13, 5, brown)
+	fillCircle(img, 4, 13, 3, pink)
+	fillCircle(img, 28, 13, 3, pink)
+
+	fillCircle(img, 16, 15, 13, brown) // head
+
+	fillEllipse(img, 16, 21, 7, 4, tan) // muzzle
+
+	// Eyes: light surround, dark iris, white highlight.
+	fillCircle(img, 11, 12, 3, tan)
+	fillCircle(img, 21, 12, 3, tan)
+	fillCircle(img, 11, 12, 2, dark)
+	fillCircle(img, 21, 12, 2, dark)
+	fillCircle(img, 12, 11, 1, white)
+	fillCircle(img, 22, 11, 1, white)
+
+	// Nostrils.
+	fillCircle(img, 14, 21, 1, dark)
+	fillCircle(img, 18, 21, 1, dark)
+
+	var buf bytes.Buffer
+	_ = png.Encode(&buf, img)
+	return buf.Bytes()
+}
+
+func fillCircle(img *image.RGBA, cx, cy, r int, c color.RGBA) {
+	for y := cy - r; y <= cy+r; y++ {
+		for x := cx - r; x <= cx+r; x++ {
+			dx, dy := x-cx, y-cy
+			if dx*dx+dy*dy <= r*r {
+				img.SetRGBA(x, y, c)
+			}
+		}
+	}
+}
+
+func fillEllipse(img *image.RGBA, cx, cy, rx, ry int, c color.RGBA) {
+	for y := cy - ry; y <= cy+ry; y++ {
+		for x := cx - rx; x <= cx+rx; x++ {
+			dx := float64(x-cx) / float64(rx)
+			dy := float64(y-cy) / float64(ry)
+			if dx*dx+dy*dy <= 1.0 {
+				img.SetRGBA(x, y, c)
+			}
+		}
+	}
+}