feature/go-rewrite : base Go avec walk GUI

- Rewrite complet en Go : exe unique sans _internal/, sans extraction temp
- GUI Windows-native via github.com/lxn/walk (TableView, TextEdit, PushButton)
- Meme fonctionnalites : check repos, pull, checkout, auto-update, logs
- build.bat : go build -ldflags "-H windowsgui -s -w" -> 9.6 Mo, zero dependance

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

platform_windows.go

@@ -0,0 +1,40 @@
+//go:build windows
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+
+	"golang.org/x/sys/windows"
+)
+
+const createNoWindow = 0x08000000
+
+// newGitCmd crée une commande git sans fenêtre console.
+func newGitCmd(ctx context.Context, args []string, cwd string) *exec.Cmd {
+	cmd := exec.CommandContext(ctx, "git", args...)
+	if cwd != "" {
+		cmd.Dir = cwd
+	}
+	cmd.SysProcAttr = &windows.SysProcAttr{
+		CreationFlags: createNoWindow,
+	}
+	return cmd
+}
+
+// relaunchAfterUpdate crée un batch qui attend 1s, relance l'exe et nettoie le .old.
+func relaunchAfterUpdate(exePath string) {
+	oldPath := exePath + ".old"
+	batPath := exePath + "_update.bat"
+	content := fmt.Sprintf(
+		"@echo off\r\ntimeout /t 1 /nobreak >nul\r\nstart \"\" \"%s\"\r\ndel \"%s\" 2>nul\r\ndel \"%%~f0\"\r\n",
+		exePath, oldPath,
+	)
+	os.WriteFile(batPath, []byte(content), 0644)
+	cmd := exec.Command("cmd", "/c", batPath)
+	cmd.SysProcAttr = &windows.SysProcAttr{CreationFlags: createNoWindow}
+	cmd.Start()
+}