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/authenticator/base32.go

@@ -0,0 +1,97 @@
+package authenticator
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// base32Alphabet is the RFC 4648 / 3548 base32 alphabet (no padding).
+const base32Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
+
+var (
+	base32EncodeTable [32]byte
+	base32DecodeTable [256]int8
+	base32CleanRE     = regexp.MustCompile(`[\s-]+`)
+	base32PadRE       = regexp.MustCompile(`=+$`)
+)
+
+func init() {
+	for i, c := range base32Alphabet {
+		base32EncodeTable[i] = byte(c)
+	}
+	for i := range base32DecodeTable {
+		base32DecodeTable[i] = -1
+	}
+	for i, c := range base32Alphabet {
+		base32DecodeTable[c] = int8(i)
+	}
+}
+
+// Base32Decode decodes a base32 string into bytes. Whitespace and dashes
+// are stripped; trailing '=' padding is ignored; input is uppercased before
+// decoding. This mirrors the lenient behavior of the original C# Base32 class.
+func Base32Decode(encoded string) ([]byte, error) {
+	encoded = base32CleanRE.ReplaceAllString(encoded, "")
+	encoded = base32PadRE.ReplaceAllString(encoded, "")
+	encoded = strings.ToUpper(encoded)
+	if encoded == "" {
+		return []byte{}, nil
+	}
+
+	const shift = 5
+	const mask = 0x1F
+
+	outLen := len(encoded) * shift / 8
+	out := make([]byte, outLen)
+
+	var buffer int
+	var bitsLeft int
+	var next int
+	for _, c := range encoded {
+		if c >= 256 || base32DecodeTable[c] < 0 {
+			return nil, fmt.Errorf("base32: illegal character %q", c)
+		}
+		buffer <<= shift
+		buffer |= int(base32DecodeTable[c]) & mask
+		bitsLeft += shift
+		if bitsLeft >= 8 {
+			out[next] = byte(buffer >> (bitsLeft - 8))
+			next++
+			bitsLeft -= 8
+		}
+	}
+	return out, nil
+}
+
+// Base32Encode encodes raw bytes as base32 with no padding.
+func Base32Encode(data []byte) string {
+	if len(data) == 0 {
+		return ""
+	}
+	const shift = 5
+	const mask = 0x1F
+
+	var sb strings.Builder
+	buffer := int(data[0])
+	next := 1
+	bitsLeft := 8
+	for bitsLeft > 0 || next < len(data) {
+		if bitsLeft < shift {
+			if next < len(data) {
+				buffer <<= 8
+				buffer |= int(data[next]) & 0xFF
+				next++
+				bitsLeft += 8
+			} else {
+				pad := shift - bitsLeft
+				buffer <<= pad
+				bitsLeft += pad
+			}
+		}
+		index := mask & (buffer >> (bitsLeft - shift))
+		bitsLeft -= shift
+		sb.WriteByte(base32EncodeTable[index])
+	}
+	return sb.String()
+}