Remove standalone fetcher, add setup tool with install/uninstall workflow

Drop claude-fetcher binary and cron job — the widget's built-in
BackgroundFetcher is the sole fetcher now. Add cmd/setup with cross-platform
install and uninstall (--uninstall): kills widget, removes binaries + autostart,
cleans Claude Code statusline setting, optionally removes config dir.

Also includes: browser-based login (chromedp), ICO wrapper for Windows tray
icon, and reduced icon size (64px).

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

cmd/widget/main.go

@@ -1,9 +1,23 @@
 package main
 
 import (
+	"log"
+	"os"
+	"path/filepath"
+
 	"git.davoryn.de/calic/claude-statusline/internal/tray"
 )
 
 func main() {
+	// Log to file next to the executable
+	exe, _ := os.Executable()
+	logPath := filepath.Join(filepath.Dir(exe), "widget.log")
+	f, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o644)
+	if err == nil {
+		log.SetOutput(f)
+		defer f.Close()
+	}
+	log.Println("widget starting")
 	tray.Run()
+	log.Println("widget exited")
 }