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

internal/linux/media.go

@@ -1,4 +1,11 @@
 //go:build linux
+
+// ============================================================
+// LINUX-ONLY FILE — Linux media playback management.
+// Uses playerctl to pause/resume media during recording.
+// The Windows equivalent is in internal/windows/
+// ============================================================
+
 package linux
 
 import (

internal/linux/overlay.go

@@ -1,5 +1,12 @@
 //go:build linux
 
+// ============================================================
+// LINUX-ONLY FILE — No-op overlay implementation for Linux.
+// On Linux, the overlay is intentionally disabled (no desktop
+// notifications). The Windows equivalent with full Win32 overlay
+// is in internal/windows/overlay.go
+// ============================================================
+
 package linux
 
 // linuxOverlay intentionally does not show system notifications. Tray status

internal/linux/process.go

@@ -1,4 +1,11 @@
 //go:build linux
+
+// ============================================================
+// LINUX-ONLY FILE — Linux process management utilities.
+// Uses syscall.Kill(pid, 0) to check if a process is running.
+// The Windows equivalent is in internal/windows/process.go
+// ============================================================
+
 package linux
 
 import "syscall"

internal/linux/startup.go

@@ -1,4 +1,12 @@
 //go:build linux
+
+// ============================================================
+// LINUX-ONLY FILE — Linux startup (autostart) management via
+// XDG Desktop Entry files (.desktop). Creates/removes autostart
+// entries and manages the application's .desktop file.
+// The Windows equivalent is in internal/windows/
+// ============================================================
+
 package linux
 
 import (