Feat/dbm20 rag (#2037)

* feat(rag): add knowledge base migration from v4.9.0 to plugin architecture

Rewrite dbm020 to backup old knowledge_bases data and preserve
external_knowledge_bases table. Add migration API endpoints and
frontend dialog so users can opt-in to auto-install LangRAG plugin
and restore their knowledge bases with original UUIDs preserved.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(rag): query marketplace for actual plugin version instead of 'latest'

The marketplace API does not support 'latest' as a version string.
Fetch the plugin info first to get latest_version, then use that
concrete version for installation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat(rag): add data-only migration option and fix dialog width

Add option to migrate knowledge base data without auto-installing
the LangRAG plugin (for offline/intranet environments). Also
narrow the migration dialog to match other confirmation dialogs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: to red and no more

* fix lint

* fix ruff lint

* feat: add external migration

* fix: show

* feat: add external plugin auto download

* feat: update migration messages for knowledge base in multiple languages

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Junyan Qin <rockchinq@gmail.com>

web/src/i18n/locales/zh-Hant.ts

@@ -722,6 +722,23 @@ const zhHant = {
     retrieverConfiguration: '檢索器配置',
     retrieverInstallInfo: '您可以從',
     retrieverMarketLink: '此處安裝知識檢索器插件',
+    migration: {
+      title: '知識庫遷移',
+      description:
+        '新版本已將知識庫重構為插件化架構，並統一內建知識庫和外部知識庫為「知識引擎」插件，需要對舊知識庫資料進行遷移。您的舊資料已自動備份在資料庫中。',
+      detected:
+        '共檢測到 {{total}} 個知識庫需要遷移（{{internal}} 個內建知識庫，{{external}} 個外部知識庫）。',
+      startWithInstall: '自動安裝插件並遷移',
+      startDataOnly: '僅遷移資料',
+      dataOnlyHint:
+        '「僅遷移資料」適合內網環境使用，請在遷移完成後自行安裝對應插件',
+      dismiss: '丟棄原數據',
+      running: '正在遷移知識庫，請稍候...',
+      success: '知識庫遷移完成',
+      error: '知識庫遷移失敗：',
+      dismissError: '操作失敗',
+      retry: '重試',
+    },
   },
   register: {
     title: '初始化 LangBot 👋',