feat: Phase 1 WinAuth Go 移植完整实现

将原 C#/.NET WinAuth 移植为 Go + Gio GUI，覆盖 Phase 1 全部功能。

核心模块：
- internal/authenticator: TOTP (Google/Microsoft/Okta) + HOTP + BattleNet + Steam，含
  enroll/sync/code 生成、Steam 交易确认轮询
- internal/config: YAML 配置 + 老版 WinAuth XML 导入（DPAPI + Password + Blowfish/PBKDF2 解密链）
- internal/crypto: 现代加密 (WAGO1) + DPAPI 跨平台封装 + 老版 Blowfish ECB
- internal/win32: 单实例 Mutex 锁 + 全局热键管理器 (RegisterHotKey + PeekMessage 泵) +
  SendInput Unicode 注入 + 剪贴板文本/CF_DIB 图像读写 + AttachThreadInput 焦点切换
- internal/hotkey: "Ctrl+Alt+G" 风格快捷键字符串解析/格式化
- internal/qr: gozxing 二维码解码 + otpauth:// URI 解析
- internal/i18n: en/zh-CN/de 三语 TOML

UI 模块 (Gio)：
- 主窗口：圆环倒计时进度条、复制按钮 + Toast 反馈、空列表占位、行分隔线
- 添加流程：vendor 菜单 + 各 vendor 独立对话框 + 二维码扫描入口（文件 / 剪贴板）
- 设置：密码加密、老版 XML 导入、每条目热键配置
- Steam：注册向导（含 captcha/email/SMS 多步）+ 交易确认窗

构建：Windows 主目标，非 Windows 平台所有 Win32 功能走 build-tag 桩实现。

internal/ui/entry_actions.go

@@ -0,0 +1,56 @@
+package ui
+
+import (
+	"image"
+	"image/color"
+
+	"gioui.org/app"
+	"gioui.org/layout"
+	"gioui.org/op/clip"
+	"gioui.org/op/paint"
+	"gioui.org/unit"
+	"gioui.org/widget/material"
+
+	"git.wxccs.org/iceking2nd/winauth-go/internal/global"
+	"git.wxccs.org/iceking2nd/winauth-go/internal/i18n"
+	"git.wxccs.org/iceking2nd/winauth-go/internal/win32"
+)
+
+// copyCodeToClipboard pushes the current OTP onto the system clipboard
+// and pops a brief toast confirming the action. Errors are surfaced via
+// the same toast so the user actually sees them.
+func (st *appState) copyCodeToClipboard(en *entry, w *app.Window) {
+	const fn = "internal.ui.appState.copyCodeToClipboard"
+	if en == nil || en.Code == "" {
+		return
+	}
+	if err := win32.SetClipboardText(en.Code); err != nil {
+		global.Log.WithField("func", fn).WithError(err).Warn("clipboard copy failed")
+		st.toast.Show(i18n.T("msg_copy_failed"), w)
+		w.Invalidate()
+		return
+	}
+	st.toast.Show(i18n.T("msg_copied"), w)
+	w.Invalidate()
+}
+
+// drawEmptyPlaceholder paints the centered "no entries yet" hint shown
+// when the entries list is empty.
+func drawEmptyPlaceholder(gtx layout.Context, th *material.Theme) layout.Dimensions {
+	return layout.Center.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		lbl := material.Body1(th, i18n.T("msg_empty_list"))
+		lbl.Color = color.NRGBA{R: 0x80, G: 0x80, B: 0x80, A: 0xff}
+		return layout.UniformInset(unit.Dp(8)).Layout(gtx, lbl.Layout)
+	})
+}
+
+// drawDivider paints a 1px-tall light-gray line across the available
+// horizontal space. Used between entries in the list.
+func drawDivider(gtx layout.Context) layout.Dimensions {
+	h := gtx.Dp(unit.Dp(1))
+	size := image.Pt(gtx.Constraints.Max.X, h)
+	defer clip.Rect{Max: size}.Push(gtx.Ops).Pop()
+	paint.ColorOp{Color: color.NRGBA{R: 0xe0, G: 0xe0, B: 0xe0, A: 0xff}}.Add(gtx.Ops)
+	paint.PaintOp{}.Add(gtx.Ops)
+	return layout.Dimensions{Size: size}
+}