feat: Support multiple knowledge base binding in pipelines (#1766)

* Initial plan

* Add multi-knowledge base support to pipelines

- Created database migration dbm010 to convert knowledge-base field from string to array
- Updated default pipeline config to use knowledge-bases array
- Updated pipeline metadata to use knowledge-base-multi-selector type
- Modified localagent.py to retrieve from multiple knowledge bases and concatenate results
- Added KNOWLEDGE_BASE_MULTI_SELECTOR type to frontend form entities
- Implemented multi-selector UI component with dialog for selecting multiple knowledge bases

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

* Add i18n translations for multi-knowledge base selector

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

* Fix prettier formatting errors in DynamicFormItemComponent

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

* Add accessibility attributes to knowledge base selector checkbox

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

* fix: minor fix

---------

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/infra/entities/form/dynamic.ts

@@ -29,6 +29,7 @@ export enum DynamicFormItemType {
   PROMPT_EDITOR = 'prompt-editor',
   UNKNOWN = 'unknown',
   KNOWLEDGE_BASE_SELECTOR = 'knowledge-base-selector',
+  KNOWLEDGE_BASE_MULTI_SELECTOR = 'knowledge-base-multi-selector',
   PLUGIN_SELECTOR = 'plugin-selector',
   BOT_SELECTOR = 'bot-selector',
 }