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/env.example.md

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+# 环境变量配置示例
+
+复制以下内容到 `.env` 文件中：
+
+```bash
+# ===========================================
+# AI Clinical Research Platform - 环境变量配置
+# ===========================================
+
+# ==================== 应用配置 ====================
+NODE_ENV=development
+PORT=3001
+HOST=0.0.0.0
+LOG_LEVEL=debug
+SERVICE_NAME=aiclinical-backend
+
+# ==================== 数据库配置 ====================
+DATABASE_URL=postgresql://postgres:postgres@localhost:5432/ai_clinical
+
+# ==================== 存储配置 ====================
+# 存储类型：local | oss
+STORAGE_TYPE=local
+
+# --- 本地存储配置（STORAGE_TYPE=local）---
+LOCAL_STORAGE_DIR=uploads
+LOCAL_STORAGE_URL=http://localhost:3001/uploads
+
+# --- 阿里云OSS配置（STORAGE_TYPE=oss）---
+# OSS_REGION=oss-cn-beijing
+# OSS_BUCKET=ai-clinical-data-dev
+# OSS_BUCKET_STATIC=ai-clinical-static-dev
+# OSS_ACCESS_KEY_ID=your-access-key-id
+# OSS_ACCESS_KEY_SECRET=your-access-key-secret
+# OSS_INTERNAL=false
+# OSS_SIGNED_URL_EXPIRES=3600
+
+# ==================== 安全配置 ====================
+JWT_SECRET=your-secret-key-change-in-production
+JWT_EXPIRES_IN=7d
+CORS_ORIGIN=http://localhost:5173
+
+# ==================== LLM API配置 ====================
+DEEPSEEK_API_KEY=
+DEEPSEEK_BASE_URL=https://api.deepseek.com
+DASHSCOPE_API_KEY=
+GEMINI_API_KEY=
+
+# ==================== 文件上传配置 ====================
+UPLOAD_MAX_SIZE=31457280
+```
+
+## OSS 开发环境配置
+
+如果要测试 OSS，将 `STORAGE_TYPE` 改为 `oss` 并填写以下配置：
+
+```bash
+STORAGE_TYPE=oss
+OSS_REGION=oss-cn-beijing
+OSS_BUCKET=ai-clinical-data-dev
+OSS_BUCKET_STATIC=ai-clinical-static-dev
+OSS_ACCESS_KEY_ID=LTAI5tBHkL39GjdLfcr77Y3f
+OSS_ACCESS_KEY_SECRET=<从安全渠道获取>
+OSS_INTERNAL=false
+OSS_SIGNED_URL_EXPIRES=3600
+```
+
+## OSS 生产环境配置（SAE）
+
+```bash
+STORAGE_TYPE=oss
+OSS_REGION=oss-cn-beijing
+OSS_BUCKET=ai-clinical-data
+OSS_BUCKET_STATIC=ai-clinical-static
+OSS_ACCESS_KEY_ID=LTAI5tBHkL39GjdLfcr77Y3f
+OSS_ACCESS_KEY_SECRET=<从安全渠道获取>
+OSS_INTERNAL=true  # 🔴 生产必须用内网
+OSS_SIGNED_URL_EXPIRES=3600
+```
+