feat: external knowledge bases (#1783)

* Initial plan

* Add backend support for external knowledge bases

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Add frontend support for external knowledge bases with tabs UI

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Add i18n translations for all languages (Traditional Chinese and Japanese)

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Update knowledge base tab list styling to match plugins page

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* perf: margin-top for kb page

* refactor: switch RetrievalResultEntry to langbot_plugin pkg ones

* feat: knowledge retriever listing and creating

* stash

* refactor: unify sync mechanism for polymorphic components

* feat: use unified retireval result struct in retrieval test page

* chore: remove unused methods

* feat: retriever icon displaying

* feat: localagent retrieval with external kbs

* chore: bump version of langbot-plugin to 0.2.0b1

* fix: i18n

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>
Co-authored-by: Junyan Qin <rockchinq@gmail.com>

web/src/i18n/locales/en-US.ts

@@ -587,6 +587,15 @@ const enUS = {
     fileName: 'File Name',
     noResults: 'No results',
     retrieveError: 'Retrieve failed',
+    builtIn: 'Built-in',
+    external: 'External',
+    addExternal: 'Add External Knowledge Base',
+    createExternalSuccess: 'External knowledge base created successfully',
+    updateExternalSuccess: 'External knowledge base updated successfully',
+    deleteExternalSuccess: 'External knowledge base deleted successfully',
+    retriever: 'Retriever',
+    selectRetriever: 'Select a retriever...',
+    retrieverConfiguration: 'Retriever Configuration',
   },
   register: {
     title: 'Initialize LangBot 👋',