Implement SyncWarden v0.1.0

Full Syncthing tray wrapper with:
- System tray with 5 icon states (idle/syncing/paused/error/disconnected)
- Syncthing REST API client with auto-discovered API key
- Long-polling event listener for real-time status
- Transfer rate monitoring, folder tracking, recent files, conflict counting
- Full context menu with folders, recent files, settings toggles
- Embedded admin panel binary (webview, requires CGO)
- OS notifications via beeep (per-event configurable)
- Syncthing process management with auto-restart
- Cross-platform installer with autostart
- CI pipeline for Linux (.deb + .tar.gz) and Windows (.zip)

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

internal/tray/open.go

@@ -0,0 +1,23 @@
+package tray
+
+import (
+	"log"
+	"os/exec"
+	"runtime"
+)
+
+// openFileManager opens the given path in the OS file manager.
+func openFileManager(path string) {
+	var cmd *exec.Cmd
+	switch runtime.GOOS {
+	case "windows":
+		cmd = exec.Command("explorer", path)
+	case "darwin":
+		cmd = exec.Command("open", path)
+	default:
+		cmd = exec.Command("xdg-open", path)
+	}
+	if err := cmd.Start(); err != nil {
+		log.Printf("failed to open file manager: %v", err)
+	}
+}