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/app/home/knowledge/knowledgeBase.module.css

@@ -5,6 +5,7 @@
 
 .knowledgeListContainer {
   width: 100%;
+  margin-top: 2rem;
   padding-left: 0.8rem;
   padding-right: 0.8rem;
   display: grid;