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/modules/asl/fulltext-screening/__tests__/api-integration-test.ts

@@ -368,5 +368,6 @@ runTests().catch((error) => {
 
 
 
+
 
 

backend/src/modules/asl/fulltext-screening/__tests__/e2e-real-test-v2.ts

@@ -309,5 +309,6 @@ runTest()
 
 
 
+
 
 

backend/src/modules/asl/fulltext-screening/__tests__/fulltext-screening-api.http

@@ -347,5 +347,6 @@ Content-Type: application/json
 
 
 
+
 
 

backend/src/modules/asl/services/screeningWorker.ts

@@ -257,7 +257,7 @@ async function processScreeningBatchWithCheckpoint(
         literature.publicationYear ? Number(literature.publicationYear) : undefined
       );
 
-      // 保存结果（使用 screeningService.ts 相同的映射方式）
+      // 保存结果（使用 upsert 保证幂等性，任务重试时覆盖而不是重复创建）
       const dbResult = {
         projectId,
         literatureId: literature.id,
@@ -294,8 +294,16 @@ async function processScreeningBatchWithCheckpoint(
         finalDecision: screeningResult.finalDecision,
       };
       
-      await prisma.aslScreeningResult.create({
-        data: dbResult,
+      // 🛡️ 使用 upsert 实现幂等性（利用 unique_project_literature 约束）
+      await prisma.aslScreeningResult.upsert({
+        where: {
+          projectId_literatureId: {
+            projectId,
+            literatureId: literature.id,
+          },
+        },
+        create: dbResult,
+        update: dbResult,
       });
 
       successCount++;

backend/src/modules/asl/workers/researchWorker.ts

@@ -67,12 +67,8 @@ export function registerResearchWorker() {
         error: error.message,
       });
 
-      // 更新任务状态为失败
-      try {
-        await researchService.executeSearch(taskId, query);
-      } catch {
-        // 忽略
-      }
+      // ❌ 已移除错误的 executeSearch 调用
+      // 任务失败后 pg-boss 会自动重试（最多3次）
 
       return { 
         success: false,