fix: Add cross-platform handling for tray, updater, and icon generation

- Add platform notes for tray startup, shortcut saving, and Linux-only settings
- Handle stat error in processRecording (missing file)
- Select correct binary name based on OS in updater
- Increase tray icon canvas size from 64 to 128 pixels
- Update frontend dist asset hash

linux_press_daemon_stub.go

@@ -1,5 +1,11 @@
 //go:build !linux
 
+// ============================================================
+// WINDOWS-ONLY FILE — Stub for the Linux press daemon.
+// On Windows, the press daemon is not used.
+// The real implementation is in linux_press_daemon.go
+// ============================================================
+
 package main
 
 func (a *App) startLinuxPressDaemon() {}