fix(backend): Resolve PgBoss infinite loop issue and cleanup unused files

Backend fixes:
- Fix PgBoss task infinite loop on SAE (root cause: missing queue table constraints)
- Add singletonKey to prevent duplicate job enqueueing
- Add idempotency check in reviewWorker (skip completed tasks)
- Add optimistic locking in reviewService (atomic status update)

Frontend fixes:
- Add isSubmitting state to prevent duplicate submissions in RVW Dashboard
- Fix API baseURL in knowledgeBaseApi (relative path)

Cleanup (removed):
- Old frontend/ directory (migrated to frontend-v2)
- python-microservice/ (unused, replaced by extraction_service)
- Root package.json and node_modules (accidentally created)
- redcap-docker-dev/ (external dependency)
- Various temporary files and outdated docs in root

New documentation:
- docs/07-运维文档/01-PgBoss队列监控与维护.md
- docs/07-运维文档/02-故障预防检查清单.md
- docs/07-运维文档/03-数据库迁移注意事项.md

Database fix applied to RDS:
- Added PRIMARY KEY to platform_schema.queue
- Added 3 missing foreign key constraints

Tested: Local build passed, RDS constraints verified

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: 4, // 🛡️ 限制连接数，避免挤占 Prisma 连接配额（RDS 限制 100）
+      max: 5, // 🛡️ 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
@@ -143,21 +143,13 @@ export class PgBossQueue implements JobQueue {
       // 存储元数据到缓存
       this.jobs.set(jobId, job)
 
-      // 确保队列存在（幂等操作）
-      try {
-        await this.boss.createQueue(type, {
-          retryLimit: 3,
-          retryDelay: 60,
-          expireInSeconds: 6 * 60 * 60 // 6小时
-        });
-      } catch (error: any) {
-        // 队列已存在时会报错，忽略
-        if (!error.message?.includes('already exists')) {
-          throw error;
-        }
-      }
+      // 📝 注意：队列已在 registerBossHandler() 中创建，这里不再重复创建
+      // 避免每次 push 都尝试 createQueue 导致重复定义
 
       // 发送任务到pg-boss
+      // ✅ 使用 singletonKey 防止同一任务被重复入队
+      const singletonKey = (data as any).taskId || jobId
+      
       const bossJobId = await this.boss.send(type, {
         ...data,
         __jobId: jobId, // 嵌入我们的jobId
@@ -165,7 +157,9 @@ export class PgBossQueue implements JobQueue {
       }, {
         retryLimit: 3,
         retryDelay: 60,
-        expireInSeconds: 6 * 60 * 60 // 6小时过期（更适合长批次任务）
+        expireInSeconds: 6 * 60 * 60, // 6小时过期（更适合长批次任务）
+        singletonKey, // ✅ 防止同一任务重复入队
+        singletonSeconds: 3600, // 1小时内不允许重复
       })
 
       console.log(`[PgBossQueue] Job pushed: ${jobId} -> pg-boss:${bossJobId} (type: ${type})`)
@@ -222,7 +216,7 @@ export class PgBossQueue implements JobQueue {
       
       await this.boss.work<Record<string, any>>(type, {
         batchSize: 1, // 每次处理1个任务
-        pollingIntervalSeconds: 1 // 每秒轮询一次
+        pollingIntervalSeconds: 2 // 每2秒轮询一次（降低频率避免竞态）
       }, async (bossJobs) => {
       // pg-boss的work handler接收的是Job数组
       const bossJob = bossJobs[0]
@@ -230,6 +224,7 @@ export class PgBossQueue implements JobQueue {
       
       const { __jobId, __createdAt, ...data } = bossJob.data
       const jobId = __jobId || randomUUID()
+      const bossJobId = bossJob.id // pg-boss 自己的 job ID
 
       // 获取或创建Job对象
       let job = this.jobs.get(jobId)
@@ -251,18 +246,33 @@ export class PgBossQueue implements JobQueue {
         job.updatedAt = new Date()
       }
 
-      console.log(`[PgBossQueue] Processing job: ${jobId} (type: ${type})`)
+      // ✅ 检查：是否已经处理过这个 job（防止重复处理）
+      const existingJob = this.jobs.get(jobId)
+      if (existingJob && existingJob.status === 'completed') {
+        console.warn(`[PgBossQueue] ⚠️ Job already completed, skipping: ${jobId} (pg-boss: ${bossJobId})`)
+        return // 跳过已完成的任务
+      }
+
+      console.log(`[PgBossQueue] Processing job: ${jobId} (pg-boss: ${bossJobId}, type: ${type})`)
 
       try {
         // 执行用户提供的处理函数
         const result = await handler(job)
 
-        // 标记为完成
+        // 标记为完成（更新内存缓存）
         await this.completeJob(jobId, result)
 
-        return result
+        // ✅ 重要：pg-boss 12.x work handler 返回 void
+        // pg-boss 会在 handler 成功返回后自动将任务标记为 completed
+        console.log(`[PgBossQueue] ✅ Job handler finished successfully: ${jobId} (pg-boss: ${bossJobId})`)
+        
+        // 打印最终状态
+        const finalJob = this.jobs.get(jobId)
+        console.log(`[PgBossQueue] Job final status: ${finalJob?.status || 'unknown'}`)
       } catch (error: any) {
-        // 标记为失败
+        console.error(`[PgBossQueue] ❌ Job handler failed: ${jobId} (pg-boss: ${bossJobId})`, error.message)
+        
+        // 标记为失败（更新内存缓存）
         await this.failJob(jobId, error.message || String(error))
         
         // 抛出错误让pg-boss处理重试