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/platform/platform.go

@@ -1,3 +1,11 @@
+// ============================================================
+// CROSS-PLATFORM FILE — This defines the Overlay interface
+// that is implemented differently on each platform:
+//   - Windows:   internal/windows/overlay.go (Win32 overlay)
+//   - Linux:     internal/linux/overlay.go (no-op)
+// This file itself is compiled on ALL platforms.
+// ============================================================
+
 package platform
 
 // Overlay defines the cross-platform interface for screen overlays

internal/platform/platform_linux.go

@@ -1,4 +1,11 @@
 //go:build linux
+
+// ============================================================
+// LINUX-ONLY FILE — Delegates all platform operations to the
+// internal/linux package (overlay, media, startup, process).
+// The Windows equivalent is platform_windows.go
+// ============================================================
+
 package platform
 
 import "wis-free-v3/internal/linux"

internal/platform/platform_windows.go

@@ -1,4 +1,11 @@
 //go:build windows
+
+// ============================================================
+// WINDOWS-ONLY FILE — Delegates all platform operations to the
+// internal/windows package (overlay, media, startup, process).
+// The Linux equivalent is platform_linux.go
+// ============================================================
+
 package platform
 
 import "wis-free-v3/internal/windows"