feat(ui): 开机自启动 + 窗口大小记忆

- win32/autostart: SetAutoStart/IsAutoStartEnabled 操作 HKCU Run 键
- win32/window_size: GetWindowSize 通过 GetWindowRect 获取窗口尺寸
- config: 新增 AutoStart、WindowWidth、WindowHeight 字段
- store: Preferences/SetPreferences 扩展支持 autoStart + windowSize
- dialog_preferences: 新增"开机自启动"复选框
- app.go: 启动时恢复窗口大小，关闭时通过 SetWindowSize 保存
- i18n: label_auto_start / hint_auto_start 三语翻译

internal/win32/window_size_windows.go

@@ -0,0 +1,25 @@
+//go:build windows
+
+package win32
+
+import (
+	"unsafe"
+)
+
+var (
+	procGetWindowRect = user32.NewProc("GetWindowRect")
+)
+
+type rect struct {
+	Left, Top, Right, Bottom int32
+}
+
+// GetWindowSize returns the width and height of the given window in pixels.
+func GetWindowSize(hwnd uintptr) (width, height int, ok bool) {
+	var r rect
+	ret, _, _ := procGetWindowRect.Call(hwnd, uintptr(unsafe.Pointer(&r)))
+	if ret == 0 {
+		return 0, 0, false
+	}
+	return int(r.Right - r.Left), int(r.Bottom - r.Top), true
+}