Rewrite in Go: static binaries, zero runtime dependencies

Replace Node.js + Python codebase with three Go binaries:
- claude-statusline: CLI status bar for Claude Code
- claude-fetcher: standalone cron job for API usage
- claude-widget: system tray icon (fyne-io/systray + fogleman/gg)

All CGO-free for trivial cross-compilation. Add nfpm .deb packaging
with autostart and cron. CI pipeline produces Linux + Windows binaries,
.deb, .tar.gz, and .zip release assets.

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

cmd/fetcher/main.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.davoryn.de/calic/claude-statusline/internal/config"
+	"git.davoryn.de/calic/claude-statusline/internal/fetcher"
+)
+
+func main() {
+	sessionKey := config.GetSessionKey()
+	if sessionKey == "" {
+		fmt.Fprintln(os.Stderr, "error: no session key (set CLAUDE_SESSION_KEY or write to "+config.SessionKeyPath()+")")
+		os.Exit(1)
+	}
+
+	cfg := config.Load()
+	data, orgID, err := fetcher.FetchUsage(sessionKey, cfg.OrgID)
+	if err != nil {
+		if data != nil {
+			// Write error state to cache so statusline can display it
+			_ = fetcher.WriteCache(data)
+		}
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
+
+	if err := fetcher.WriteCache(data); err != nil {
+		fmt.Fprintf(os.Stderr, "error writing cache: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Persist discovered org ID
+	if orgID != "" && orgID != cfg.OrgID {
+		cfg.OrgID = orgID
+		_ = config.Save(cfg)
+	}
+
+	parsed := fetcher.ParseUsage(data)
+	if parsed.FiveHourPct > 0 {
+		fmt.Printf("5h: %d%%", parsed.FiveHourPct)
+		if parsed.FiveHourResetsIn != "" {
+			fmt.Printf(" (resets in %s)", parsed.FiveHourResetsIn)
+		}
+		fmt.Println()
+	}
+	if parsed.SevenDayPct > 0 {
+		fmt.Printf("7d: %d%%", parsed.SevenDayPct)
+		if parsed.SevenDayResetsIn != "" {
+			fmt.Printf(" (resets in %s)", parsed.SevenDayResetsIn)
+		}
+		fmt.Println()
+	}
+}