feat(iit): Complete Day 3 - WeChat Work integration and URL verification

Summary:
- Implement WechatService (314 lines, push notifications)
- Implement WechatCallbackController (501 lines, async reply mode)
- Complete iit_quality_check Worker with WeChat notifications
- Configure WeChat routes (GET + POST /wechat/callback)
- Configure natapp tunnel for local development
- WeChat URL verification test passed

Technical Highlights:
- Async reply mode to avoid 5-second timeout
- Message encryption/decryption using @wecom/crypto
- Signature verification using getSignature
- natapp tunnel: https://iit.nat100.top
- Environment variables configuration completed

Technical Challenges Solved:
- Fix environment variable naming (WECHAT_CORP_SECRET)
- Fix @wecom/crypto import (createRequire for CommonJS)
- Fix decrypt function parameters (2 params, not 4)
- Fix Token character recognition (lowercase l vs digit 1)
- Regenerate EncodingAESKey (43 chars, correct format)
- Configure natapp for internal network penetration

Test Results:
- WeChat developer tool verification: PASSED
- Return status: request success
- HTTP 200, decrypted 23 characters correctly
- Backend logs: URL verification successful

Documentation:
- Add Day3 WeChat integration development record
- Update MVP development task list (Day 2-3 completed)
- Update module status guide (v1.2 -> v1.3)
- Overall completion: 35% -> 50%

Progress:
- Module completion: 35% -> 50%
- Day 3 development: COMPLETED
- Ready for end-to-end testing (REDCap -> WeChat)

backend/package.json

@@ -31,6 +31,7 @@
     "@fastify/multipart": "^9.2.1",
     "@prisma/client": "^6.17.0",
     "@types/form-data": "^2.2.1",
+    "@wecom/crypto": "^1.0.1",
     "ajv": "^8.17.1",
     "axios": "^1.12.2",
     "bullmq": "^5.65.0",
@@ -49,12 +50,14 @@
     "tiktoken": "^1.0.22",
     "winston": "^3.18.3",
     "xlsx": "^0.18.5",
+    "xml2js": "^0.6.2",
     "zod": "^4.1.12"
   },
   "devDependencies": {
     "@types/js-yaml": "^4.0.9",
     "@types/node": "^24.7.1",
     "@types/winston": "^2.4.4",
+    "@types/xml2js": "^0.4.14",
     "better-sqlite3": "^12.4.6",
     "nodemon": "^3.1.10",
     "pino-pretty": "^13.1.1",