feat(ui): 主题切换 + 语言持久化 + About 对话框

- 新增 light/dark 主题调色板与 Windows 注册表系统主题探测
- 偏好设置对话框：主题三选一 + 语言下拉(en/zh-CN/de)，即时生效
- 持久化 Language/Theme/AutoLockMinutes/MinimizeToTray 至 YAML 顶层
- 启动时按 config 中保存的语言初始化 i18n
- About 对话框展示 version/runtime/项目地址/许可证
- 全部硬编码颜色迁移到 themePalette，为深色模式做准备

internal/i18n/locales/zh-CN.toml

@@ -367,3 +367,55 @@ other = "二维码扫描失败：%s"
 
 [msg_clipboard_no_image]
 other = "剪贴板中没有图片"
+
+# --- 偏好设置 ---
+
+[menu_preferences]
+other = "偏好设置..."
+
+[dialog_preferences_title]
+other = "偏好设置"
+
+[label_theme]
+other = "主题"
+
+[theme_system]
+other = "跟随系统"
+
+[theme_light]
+other = "浅色"
+
+[theme_dark]
+other = "深色"
+
+[label_language]
+other = "语言"
+
+# --- 关于对话框 ---
+
+[dialog_about_title]
+other = "关于 WinAuth"
+
+[about_app_name]
+other = "WinAuth (Go 版) — TOTP/HOTP 验证器"
+
+[about_version_label]
+other = "版本"
+
+[about_runtime_label]
+other = "运行时"
+
+[about_project_label]
+other = "项目主页"
+
+[about_project_url]
+other = "https://git.wxccs.org/iceking2nd/winauth-go"
+
+[about_license_label]
+other = "许可证"
+
+[about_license_value]
+other = "MIT"
+
+[about_credits]
+other = "原版 WinAuth 由 Colin Mackie 创作。Go 移植由本项目作者维护。"