feat(ui): 导出/备份 — otpauth URI 列表 + 加密备份导出/恢复

- qr/export.go: EntryToOtpAuth + OtpAuth.URI，将 config.Entry 反向
  转换为标准 otpauth:// URI（Battle.Net/Steam 标记为 partial）
- dialog_export.go: Tab 切换对话框，otpauth URI 列表可复制 +
  加密备份文件导出（独立密码，0o600 权限）
- dialog_restore_backup.go: 从 .winauth.bak 恢复，密码验证后合并
- settings_menu: 新增 Export / Restore Backup 菜单项
- i18n: en/zh-CN/de 三语翻译

internal/i18n/locales/de.toml

@@ -523,3 +523,53 @@ other = "Passwortschutz aktivieren"
 
 [btn_welcome_skip]
 other = "Vorerst überspringen"
+
+# --- Export / Backup ---
+
+[menu_export]
+other = "Exportieren..."
+
+[menu_restore_backup]
+other = "Backup wiederherstellen..."
+
+[dialog_export_title]
+other = "Authentifikatoren exportieren"
+
+[export_tab_otpauth]
+other = "otpauth://-URIs"
+
+[export_tab_backup]
+other = "Verschlüsseltes Backup"
+
+[export_otpauth_intro]
+other = "Unten stehen die Standard-otpauth://-URIs für jeden Eintrag. Sie können in andere Authenticator-Apps (Google Authenticator, Authy usw.) importiert werden."
+
+[export_partial_warning]
+other = "Teilweiser Export — herstellerspezifische Felder fehlen"
+
+[export_backup_intro]
+other = "Schreibe eine verschlüsselte Backupdatei, die auf jedem Rechner wiederhergestellt werden kann. Wähle ein starkes Passwort — es ist NICHT mit dem aktuellen WinAuth-Passwort verknüpft."
+
+[label_backup_path]
+other = "Pfad zur Backupdatei"
+
+[btn_export]
+other = "Exportieren"
+
+[msg_empty_backup_path]
+other = "Bitte den Pfad zur Backupdatei eingeben."
+
+[msg_export_done]
+other = "Backup erfolgreich exportiert."
+
+[msg_export_failed]
+other = "Export fehlgeschlagen: %s"
+
+[dialog_restore_backup_title]
+other = "Backup wiederherstellen"
+
+[restore_backup_intro]
+other = "Wähle eine verschlüsselte Backupdatei (.winauth.bak) und gib das beim Erstellen gesetzte Passwort ein. Einträge werden an die aktuelle Liste angehängt."
+
+[msg_restore_done]
+other = "Backup wiederhergestellt."

internal/i18n/locales/en.toml

@@ -511,3 +511,67 @@ other = "Change icon..."
 
 [dialog_icon_picker_title]
 other = "Choose icon"
+
+# --- First-run welcome dialog ---
+
+[dialog_welcome_title]
+other = "Welcome to WinAuth"
+
+[msg_welcome_intro]
+other = "Choose whether to encrypt the list of authenticators stored on disk. Encryption protects the file with a password of your choice. You can change this later in Settings."
+
+[btn_welcome_enable_password]
+other = "Enable password protection"
+
+[btn_welcome_skip]
+other = "Skip for now"
+
+# --- Export / backup ---
+
+[menu_export]
+other = "Export..."
+
+[menu_restore_backup]
+other = "Restore backup..."
+
+[dialog_export_title]
+other = "Export authenticators"
+
+[export_tab_otpauth]
+other = "otpauth:// URIs"
+
+[export_tab_backup]
+other = "Encrypted backup"
+
+[export_otpauth_intro]
+other = "Below are standard otpauth:// URIs for each entry. You can import them into other authenticator apps (Google Authenticator, Authy, etc.)."
+
+[export_partial_warning]
+other = "partial export — vendor-specific fields omitted"
+
+[export_backup_intro]
+other = "Write an encrypted backup file that can be restored on any machine. Choose a strong password — it is NOT linked to your current WinAuth password."
+
+[label_backup_path]
+other = "Backup file path"
+
+[btn_export]
+other = "Export"
+
+[msg_empty_backup_path]
+other = "Please enter a backup file path."
+
+[msg_export_done]
+other = "Backup exported successfully."
+
+[msg_export_failed]
+other = "Export failed: %s"
+
+[dialog_restore_backup_title]
+other = "Restore from backup"
+
+[restore_backup_intro]
+other = "Select an encrypted backup file (.winauth.bak) and enter the password that was set when it was created. Entries will be appended to your current list."
+
+[msg_restore_done]
+other = "Backup restored."

internal/i18n/locales/zh-CN.toml

@@ -509,3 +509,67 @@ other = "更换图标..."
 
 [dialog_icon_picker_title]
 other = "选择图标"
+
+# --- 首次启动欢迎 ---
+
+[dialog_welcome_title]
+other = "欢迎使用 WinAuth"
+
+[msg_welcome_intro]
+other = "选择是否对磁盘上存储的验证器列表进行加密。加密将使用你选择的密码保护文件。你可以在设置中随时更改。"
+
+[btn_welcome_enable_password]
+other = "启用密码保护"
+
+[btn_welcome_skip]
+other = "暂时跳过"
+
+# --- 导出 / 备份 ---
+
+[menu_export]
+other = "导出..."
+
+[menu_restore_backup]
+other = "恢复备份..."
+
+[dialog_export_title]
+other = "导出验证器"
+
+[export_tab_otpauth]
+other = "otpauth:// URI"
+
+[export_tab_backup]
+other = "加密备份"
+
+[export_otpauth_intro]
+other = "以下是每个条目的标准 otpauth:// URI，可导入到其他验证器应用（Google Authenticator、Authy 等）。"
+
+[export_partial_warning]
+other = "部分导出 — 厂商专用字段已省略"
+
+[export_backup_intro]
+other = "将加密备份文件写入磁盘，可在任何机器上恢复。请选择强密码——此密码与当前 WinAuth 密码无关。"
+
+[label_backup_path]
+other = "备份文件路径"
+
+[btn_export]
+other = "导出"
+
+[msg_empty_backup_path]
+other = "请输入备份文件路径。"
+
+[msg_export_done]
+other = "备份导出成功。"
+
+[msg_export_failed]
+other = "导出失败：%s"
+
+[dialog_restore_backup_title]
+other = "从备份恢复"
+
+[restore_backup_intro]
+other = "选择加密备份文件（.winauth.bak）并输入创建时设置的密码。条目将追加到当前列表。"
+
+[msg_restore_done]
+other = "备份已恢复。"