Enhance simulation configuration and management features

- Added support for a `max_rounds` parameter in simulation API, allowing users to limit the number of simulation rounds, improving control over simulation duration.
- Updated README.md to reflect the new `max_rounds` parameter and its usage in simulation requests.
- Enhanced error handling for `max_rounds` input validation to ensure it is a positive integer.
- Modified simulation runner and related scripts to incorporate `max_rounds` functionality, ensuring consistent application across Twitter and Reddit simulations.
- Improved logging to indicate when the number of rounds is truncated due to the `max_rounds` setting, enhancing traceability during simulation execution.

backend/README.md

@@ -554,7 +554,8 @@ backend/
 ```json
 {
   "simulation_id": "sim_10b494550540",
-  "platform": "parallel"
+  "platform": "parallel",
+  "max_rounds": 100
 }
 ```
 
@@ -562,6 +563,7 @@ backend/
 |------|------|------|--------|------|
 | simulation_id | String | 是 | - | 模拟ID |
 | platform | String | 否 | parallel | 运行平台: twitter/reddit/parallel |
+| max_rounds | Integer | 否 | - | 最大模拟轮数，用于截断过长的模拟。如果配置中的轮数超过此值，将被截断 |
 
 **返回示例**:
 ```json
@@ -573,11 +575,15 @@ backend/
     "process_pid": 12345,
     "twitter_running": true,
     "reddit_running": true,
-    "started_at": "2025-12-02T11:00:00"
+    "started_at": "2025-12-02T11:00:00",
+    "total_rounds": 100,
+    "max_rounds_applied": 100
   }
 }
 ```
 
+> **说明**: `max_rounds_applied` 字段仅在指定了 `max_rounds` 参数时返回，表示实际应用的最大轮数限制。
+
 ---
 
 #### 5. 停止模拟
@@ -1502,12 +1508,13 @@ curl -X POST http://localhost:5001/api/simulation/prepare/status \
 
 # 等待status=completed
 
-# Step 7: 启动模拟
+# Step 7: 启动模拟（可选指定max_rounds限制轮数）
 curl -X POST http://localhost:5001/api/simulation/start \
   -H "Content-Type: application/json" \
   -d '{
     "simulation_id": "sim_xxx",
-    "platform": "parallel"
+    "platform": "parallel",
+    "max_rounds": 50
   }'
 
 # Step 8: 实时查询运行状态