feat(backup): add pre-migration backup, periodic backup, backfill warning, and backup management UI

Four improvements to the database backup mechanism:

1. Auto backup before schema migration - creates a snapshot when
   upgrading from an older database version, providing a safety net
   beyond the existing SAVEPOINT rollback mechanism.

2. Periodic startup backup - checks on app launch whether the latest
   backup is older than 24 hours and creates a new one if needed,
   ensuring all users have recent backups regardless of usage patterns.

3. Backfill failure notification - switch now returns SwitchResult with
   warnings instead of silently ignoring backfill errors, so users are
   informed when their manual config changes may not have been saved.

4. Backup management UI - new BackupListSection in Settings > Data
   Management showing all backup snapshots with restore capability,
   including a confirmation dialog and automatic safety backup before
   restore.

src/i18n/locales/en.json

@@ -174,7 +174,8 @@
     "openclawModelsRegistered": "Models have been registered to /model list",
     "openclawDefaultModelSet": "Set as default model",
     "openclawDefaultModelSetFailed": "Failed to set default model",
-    "openclawNoModels": "No models configured"
+    "openclawNoModels": "No models configured",
+    "backfillWarning": "Switched successfully, but failed to save changes back to the previous provider"
   },
   "confirm": {
     "deleteProvider": "Delete Provider",
@@ -295,6 +296,18 @@
     "selectFileFailed": "Please choose a valid SQL backup file",
     "configCorrupted": "SQL file may be corrupted or invalid",
     "backupId": "Backup ID",
+    "backupManager": {
+      "title": "Database Backups",
+      "description": "Automatic database snapshots for restoring to a previous state",
+      "empty": "No backups yet",
+      "restore": "Restore",
+      "restoring": "Restoring...",
+      "confirmTitle": "Confirm Restore",
+      "confirmMessage": "Restoring this backup will overwrite the current database. A safety backup will be created first.",
+      "restoreSuccess": "Restore successful! Safety backup created",
+      "restoreFailed": "Restore failed",
+      "safetyBackupId": "Safety Backup ID"
+    },
     "webdavSync": {
       "title": "WebDAV Cloud Sync",
       "description": "Sync database and skill configurations across devices via WebDAV.",

src/i18n/locales/ja.json

@@ -174,7 +174,8 @@
     "openclawModelsRegistered": "モデルが /model リストに登録されました",
     "openclawDefaultModelSet": "デフォルトモデルに設定しました",
     "openclawDefaultModelSetFailed": "デフォルトモデルの設定に失敗しました",
-    "openclawNoModels": "モデルが設定されていません"
+    "openclawNoModels": "モデルが設定されていません",
+    "backfillWarning": "切り替え成功しましたが、前のプロバイダーへの設定保存に失敗しました"
   },
   "confirm": {
     "deleteProvider": "プロバイダーを削除",
@@ -295,6 +296,18 @@
     "selectFileFailed": "有効な SQL バックアップファイルを選択してください",
     "configCorrupted": "SQL ファイルが壊れているか形式が無効な可能性があります",
     "backupId": "バックアップ ID",
+    "backupManager": {
+      "title": "データベースバックアップ",
+      "description": "以前の状態に復元するための自動データベーススナップショット",
+      "empty": "バックアップはまだありません",
+      "restore": "復元",
+      "restoring": "復元中...",
+      "confirmTitle": "バックアップの復元を確認",
+      "confirmMessage": "このバックアップを復元すると現在のデータベースが上書きされます。安全バックアップが先に作成されます。",
+      "restoreSuccess": "復元成功！安全バックアップが作成されました",
+      "restoreFailed": "復元に失敗しました",
+      "safetyBackupId": "安全バックアップID"
+    },
     "webdavSync": {
       "title": "WebDAV クラウド同期",
       "description": "WebDAV を使ってデバイス間でデータベースとスキル設定を同期します。",

src/i18n/locales/zh.json

@@ -174,7 +174,8 @@
     "openclawModelsRegistered": "模型已注册到 /model 列表",
     "openclawDefaultModelSet": "已设为默认模型",
     "openclawDefaultModelSetFailed": "设置默认模型失败",
-    "openclawNoModels": "该供应商没有配置模型"
+    "openclawNoModels": "该供应商没有配置模型",
+    "backfillWarning": "切换成功，但旧供应商配置回填失败，您手动修改的配置可能未保存"
   },
   "confirm": {
     "deleteProvider": "删除供应商",
@@ -295,6 +296,18 @@
     "selectFileFailed": "请选择有效的 SQL 备份文件",
     "configCorrupted": "SQL 文件可能已损坏或格式不正确",
     "backupId": "备份ID",
+    "backupManager": {
+      "title": "数据库备份",
+      "description": "自动备份的数据库快照，可用于恢复到之前的状态",
+      "empty": "暂无备份",
+      "restore": "恢复",
+      "restoring": "恢复中...",
+      "confirmTitle": "确认恢复备份",
+      "confirmMessage": "恢复到此备份将覆盖当前数据库。恢复前会自动创建安全备份。",
+      "restoreSuccess": "恢复成功！安全备份已创建",
+      "restoreFailed": "恢复失败",
+      "safetyBackupId": "安全备份ID"
+    },
     "webdavSync": {
       "title": "WebDAV 云同步",
       "description": "通过 WebDAV 在多设备间同步数据库和技能配置。",