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

backend/src/common/auth/jwt.service.ts

@@ -202,3 +202,4 @@ export const jwtService = new JWTService();
 
 
 
+

backend/src/common/jobs/PgBossQueue.ts

@@ -50,7 +50,7 @@ export class PgBossQueue implements JobQueue {
     this.boss = new PgBoss({
       connectionString,
       schema, // 使用platform_schema
-      max: 10, // 最大连接数
+      max: 4, // 🛡️ 限制连接数，避免挤占 Prisma 连接配额（RDS 限制 100）
       application_name: 'aiclinical-queue',
       
       // 调度配置
@@ -61,6 +61,17 @@ export class PgBossQueue implements JobQueue {
       maintenanceIntervalSeconds: 300, // 每5分钟运行维护任务
     })
 
+    // 🛡️ 全局错误监听：防止未捕获错误导致进程崩溃
+    this.boss.on('error', (err: any) => {
+      // 静默处理 duplicate key 错误（队列并发初始化时的正常现象）
+      if (err.code === '23505' && err.constraint === 'queue_pkey') {
+        console.log(`[PgBossQueue] ℹ️ Queue concurrency conflict auto-resolved: ${err.detail}`);
+      } else {
+        console.error('[PgBossQueue] ❌ Critical error:', err);
+        // 记录到日志但不崩溃进程
+      }
+    });
+
     console.log('[PgBossQueue] Initialized with schema:', schema)
   }
 
@@ -192,13 +203,22 @@ export class PgBossQueue implements JobQueue {
     console.log(`[PgBossQueue] 🔧 开始注册 Handler: ${type}`);
     
     try {
-      // pg-boss 9.x 需要显式创建队列
-      await this.boss.createQueue(type, {
-        retryLimit: 3,
-        retryDelay: 60,
-        expireInSeconds: 6 * 60 * 60 // 6小时
-      });
-      console.log(`[PgBossQueue] ✅ Queue created: ${type}`);
+      // pg-boss 9.x 需要显式创建队列（幂等操作）
+      try {
+        await this.boss.createQueue(type, {
+          retryLimit: 3,
+          retryDelay: 60,
+          expireInSeconds: 6 * 60 * 60 // 6小时
+        });
+        console.log(`[PgBossQueue] ✅ Queue created: ${type}`);
+      } catch (createError: any) {
+        // 队列已存在时会报 duplicate key 错误，忽略
+        if (createError.code === '23505' || createError.message?.includes('already exists')) {
+          console.log(`[PgBossQueue] ℹ️ Queue already exists: ${type}`);
+        } else {
+          throw createError;
+        }
+      }
       
       await this.boss.work<Record<string, any>>(type, {
         batchSize: 1, // 每次处理1个任务

backend/src/common/jobs/utils.ts

@@ -332,5 +332,6 @@ export function getBatchItems<T>(
 
 
 
+
 
 

backend/src/common/prompt/prompt.types.ts

@@ -85,3 +85,4 @@ export interface VariableValidation {
 
 
 
+

backend/src/common/rag/ChunkService.ts

@@ -355,3 +355,4 @@ export default ChunkService;
 
 
 
+

backend/src/common/rag/DifyClient.ts

@@ -51,3 +51,4 @@ export const DifyClient = DeprecatedDifyClient;
 
 
 
+

backend/src/common/streaming/OpenAIStreamAdapter.ts

@@ -206,3 +206,4 @@ export function createOpenAIStreamAdapter(
 
 
 
+

backend/src/common/streaming/StreamingService.ts

@@ -212,3 +212,4 @@ export async function streamChat(
 
 
 
+

backend/src/common/streaming/index.ts

@@ -30,3 +30,4 @@ export { THINKING_TAGS } from './types';
 
 
 
+

backend/src/common/streaming/types.ts

@@ -105,3 +105,4 @@ export type SSEEventType =
 
 
 
+