docs(iit): Add IIT Manager Agent V2.9 development plan with multi-agent architecture

Features:
- Add V2.9 enhancements: Cron Skill, User Profiling, Feedback Loop, Multi-Intent Handling
- Create modular development plan documents (database, engines, services, memory, tasks)
- Add V2.5/V2.6/V2.8/V2.9 design documents for architecture evolution
- Add system design white papers and implementation guides

Architecture:
- Dual-Brain Architecture (SOP + ReAct engines)
- Three-layer memory system (Flow Log, Hot Memory, History Book)
- ProfilerService for personalized responses
- SchedulerService with Cron Skill support

Also includes:
- Frontend nginx config updates
- Backend test scripts for WeChat signature
- Database backup files

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend-v2/nginx.conf

@@ -102,6 +102,29 @@ http {
 
         # ==================== API 反向代理 ====================
 
+        # 微信服务号回调代理（关键！微信验证需要）
+        location /wechat/ {
+            # 代理到后端服务
+            proxy_pass http://backend;
+            
+            # 保留原始请求信息
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+            
+            # 超时配置
+            proxy_connect_timeout 60s;
+            proxy_send_timeout 60s;
+            proxy_read_timeout 60s;
+            
+            # 缓冲配置
+            proxy_buffering off;
+            
+            # HTTP 1.1
+            proxy_http_version 1.1;
+        }
+
         # 后端 API 代理（关键配置）
         location /api/ {
             # 文件上传大小限制（PKB 文档上传等场景）