feat(platform): Complete Postgres-Only architecture refactoring (Phase 1-7)

Major Changes:
- Implement Platform-Only architecture pattern (unified task management)
- Add PostgresCacheAdapter for unified caching (platform_schema.app_cache)
- Add PgBossQueue for job queue management (platform_schema.job)
- Implement CheckpointService using job.data (generic for all modules)
- Add intelligent threshold-based dual-mode processing (THRESHOLD=50)
- Add task splitting mechanism (auto chunk size recommendation)
- Refactor ASL screening service with smart mode selection
- Refactor DC extraction service with smart mode selection
- Register workers for ASL and DC modules

Technical Highlights:
- All task management data stored in platform_schema.job.data (JSONB)
- Business tables remain clean (no task management fields)
- CheckpointService is generic (shared by all modules)
- Zero code duplication (DRY principle)
- Follows 3-layer architecture principle
- Zero additional cost (no Redis needed, save 8400 CNY/year)

Code Statistics:
- New code: ~1750 lines
- Modified code: ~500 lines
- Test code: ~1800 lines
- Documentation: ~3000 lines

Testing:
- Unit tests: 8/8 passed
- Integration tests: 2/2 passed
- Architecture validation: passed
- Linter errors: 0

Files:
- Platform layer: PostgresCacheAdapter, PgBossQueue, CheckpointService, utils
- ASL module: screeningService, screeningWorker
- DC module: ExtractionController, extractionWorker
- Tests: 11 test files
- Docs: Updated 4 key documents

Status: Phase 1-7 completed, Phase 8-9 pending

backend/src/common/jobs/JobFactory.ts

@@ -1,22 +1,25 @@
 import { JobQueue } from './types.js'
 import { MemoryQueue } from './MemoryQueue.js'
+import { PgBossQueue } from './PgBossQueue.js'
 
 /**
  * 任务队列工厂类
  * 
  * 根据环境变量自动选择队列实现：
  * - QUEUE_TYPE=memory: 使用MemoryQueue（内存队列）
- * - QUEUE_TYPE=database: 使用DatabaseQueue（数据库队列，待实现）
+ * - QUEUE_TYPE=pgboss: 使用PgBossQueue（Postgres队列）
+ * - QUEUE_TYPE=database: 别名，指向pgboss
  * 
  * 零代码切换：
  * - 本地开发：不配置QUEUE_TYPE，默认使用memory
- * - 云端部署：配置QUEUE_TYPE=database（多实例共享）
+ * - Postgres-Only架构：配置QUEUE_TYPE=pgboss
+ * - 多实例部署：配置QUEUE_TYPE=pgboss（自动负载均衡）
  * 
  * @example
  * ```typescript
  * import { jobQueue } from '@/common/jobs'
  * 
- * // 业务代码不关心是memory还是database
+ * // 业务代码不关心具体实现
  * const job = await jobQueue.push('asl:screening', { projectId: 123 })
  * ```
  */
@@ -43,10 +46,9 @@ export class JobFactory {
       case 'memory':
         return this.createMemoryQueue()
       
-      case 'database':
-        // TODO: 实现DatabaseQueue
-        console.warn('[JobFactory] DatabaseQueue not implemented yet, fallback to MemoryQueue')
-        return this.createMemoryQueue()
+      case 'pgboss':
+      case 'database': // 别名
+        return this.createPgBossQueue()
       
       default:
         console.warn(`[JobFactory] Unknown QUEUE_TYPE: ${queueType}, fallback to memory`)
@@ -72,6 +74,37 @@ export class JobFactory {
     return queue
   }
 
+  /**
+   * 创建PgBoss队列
+   */
+  private static createPgBossQueue(): PgBossQueue {
+    const databaseUrl = process.env.DATABASE_URL
+
+    if (!databaseUrl) {
+      throw new Error(
+        '[JobFactory] DATABASE_URL is required when QUEUE_TYPE=pgboss'
+      )
+    }
+
+    console.log('[JobFactory] Using PgBossQueue (Postgres-Only架构)')
+
+    const queue = new PgBossQueue(databaseUrl, 'platform_schema')
+
+    // 启动队列（异步）
+    queue.start().catch(err => {
+      console.error('[JobFactory] Failed to start PgBossQueue:', err)
+    })
+
+    // 定期清理缓存中的已完成任务
+    if (process.env.NODE_ENV !== 'test') {
+      setInterval(() => {
+        queue.cleanup()
+      }, 60 * 60 * 1000) // 每小时清理一次
+    }
+
+    return queue
+  }
+
   /**
    * 重置实例（用于测试）
    */