feat(platform): Fix pg-boss queue conflict and add safety standards

Summary:
- Fix pg-boss queue conflict (duplicate key violation on queue_pkey)
- Add global error listener to prevent process crash
- Reduce connection pool from 10 to 4
- Add graceful shutdown handling (SIGTERM/SIGINT)
- Fix researchWorker recursive call bug in catch block
- Make screeningWorker idempotent using upsert

Security Standards (v1.1):
- Prohibit recursive retry in Worker catch blocks
- Prohibit payload bloat (only store fileKey/ID in job.data)
- Require Worker idempotency (upsert + unique constraint)
- Recommend task-specific expireInSeconds settings
- Document graceful shutdown pattern

New Features:
- PKB signed URL endpoint for document preview/download
- pg_bigm installation guide for Docker
- Dockerfile.postgres-with-extensions for pgvector + pg_bigm

Documentation:
- Update Postgres-Only async task processing guide (v1.1)
- Add troubleshooting SQL queries
- Update safety checklist

Tested: Local verification passed

frontend-v2/src/shared/components/Chat/AIStreamChat.tsx

@@ -479,3 +479,4 @@ export default AIStreamChat;
 
 
 
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frontend-v2/src/shared/components/Chat/ConversationList.tsx

@@ -179,3 +179,4 @@ export default ConversationList;
 
 
 
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frontend-v2/src/shared/components/Chat/hooks/index.ts

@@ -31,3 +31,4 @@ export type {
 
 
 
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frontend-v2/src/shared/components/Chat/hooks/useAIStream.ts

@@ -323,3 +323,4 @@ export default useAIStream;
 
 
 
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frontend-v2/src/shared/components/Chat/hooks/useConversations.ts

@@ -252,3 +252,4 @@ export default useConversations;
 
 
 
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frontend-v2/src/shared/components/Chat/styles/ai-stream-chat.css

@@ -287,3 +287,4 @@
 
 
 
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frontend-v2/src/shared/components/Chat/styles/conversation-list.css

@@ -223,3 +223,4 @@
 
 
 
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frontend-v2/src/shared/components/Chat/styles/thinking.css

@@ -160,3 +160,4 @@
 
 
 
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frontend-v2/src/shared/components/index.ts

@@ -73,5 +73,6 @@ export { default as Placeholder } from './Placeholder';
 
 
 
+