feat(storage): integrate Alibaba Cloud OSS for file persistence - Add OSSAdapter and LocalAdapter with StorageFactory pattern - Integrate PKB module with OSS upload - Rename difyDocumentId to storageKey - Create 4 OSS buckets and development specification

backend/package.json

@@ -33,6 +33,7 @@
     "@types/form-data": "^2.2.1",
     "@wecom/crypto": "^1.0.1",
     "ajv": "^8.17.1",
+    "ali-oss": "^6.23.0",
     "axios": "^1.12.2",
     "bcryptjs": "^2.4.3",
     "bullmq": "^5.65.0",
@@ -58,6 +59,7 @@
     "zod": "^4.1.12"
   },
   "devDependencies": {
+    "@types/ali-oss": "^6.23.1",
     "@types/bcryptjs": "^2.4.6",
     "@types/js-yaml": "^4.0.9",
     "@types/jsonwebtoken": "^9.0.7",