📝 docs(prd): update business process documentation

- add promotion distribution process (N) and its sub-processes: invitation reward mechanism, distribution channel management, commission settlement process, withdrawal management function
- connect promotion distribution with existing data reporting and system management processes
- update core business process sequence to include promotion distribution after points management
- adjust process loop notation from N→O→P→M to O→P→Q→M for consistency

docs/prd.md

@@ -261,10 +261,19 @@ graph TD
     I --> I3[积分兑换]
     I --> I4[商城订单]
 
+    E1 --> N[推广分销流程]
+    I1 --> N
+
+    N --> N1[邀请奖励机制]
+    N --> N2[分销渠道管理]
+    N --> N3[佣金结算流程]
+    N --> N4[提现管理功能]
+
     F2 --> J[数据报表流程]
     G3 --> J
     H2 --> J
     I4 --> J
+    N3 --> J
 
     J --> J1[报表生成]
     J --> J2[数据导出]
@@ -284,19 +293,20 @@ graph TD
     G4 --> L
     H4 --> L
     I3 --> L
+    N4 --> L
     J2 --> L
     K4 --> L
 
     L --> M[系统持续运营]
-    M --> N[数据驱动优化]
-    N --> O[用户体验提升]
-    O --> P[业务增长]
-    P --> M
+    M --> O[数据驱动优化]
+    O --> P[用户体验提升]
+    P --> Q[业务增长]
+    Q --> M
 ```
 
 **业务流程说明**:
 - **起点**: 系统启动和基础配置，建立多端用户体系
-- **核心流程**: 房源管理 → 订单管理 → 支付结算 → 积分管理
+- **核心流程**: 房源管理 → 订单管理 → 支付结算 → 积分管理 → 推广分销
 - **支撑流程**: 数据报表和系统管理提供运营支撑
 - **闭环**: 业务数据驱动系统优化，实现持续增长