feat(user): add user creation endpoint for superusers

- Add new `/userMgr/create` endpoint for superusers to create users with specified types
- Update AddUser function to accept user type parameter
- Add documentation for the new endpoint in api.md
- Remove debug log comment in auth.go

docs/api.md

@@ -33,6 +33,7 @@ All API responses are returned in JSON format:
 **Endpoint:** `/register`  
 **Method:** POST  
 **Content-Type:** application/json
+**Permission Level:** None
 
 **Request Headers:**
 ```
@@ -77,7 +78,8 @@ X-Timestamp: 1704067200000
 
 **Endpoint:** `/login`  
 **Method:** POST  
-**Content-Type:** application/json
+**Content-Type:** application/json  
+**Permission Level:** None
 
 **Request Headers:**
 ```
@@ -122,6 +124,7 @@ X-Timestamp: 1704067200000
 **Endpoint:** `/logout`  
 **Method:** GET  
 **Auth Required:** Yes (token)
+**Permission Level:** None
 
 **Request Headers:**
 ```
@@ -143,12 +146,51 @@ X-Timestamp: 1704067200000
 
 ---
 
+## Create User
+
+**Endpoint**: `/userMgr/create`  
+**Method**: POST  
+**Content-Type**: application/json  
+**Auth Required**: Yes (token)  
+**Permission Level**: Superuser
+
+**Request Headers**:
+```
+X-Token: your_token
+X-Timestamp: 1704067200000
+```
+
+**Request Body**:
+```json
+{
+  "username": "new_user",
+  "passwd": "NewPass123!",
+  "type": "admin"
+}
+```
+
+**Response**:
+```json
+{
+  "success": true,
+  "message": "user created successfully",
+  "data": {
+    "userID": 2,
+    "username": "new_user",
+    "type": "admin"
+  }
+}
+```
+
+---
+
 ## Create frpc Instance
 
 **Endpoint:** `/frpcAct/instanceMgr/create`  
 **Method:** POST  
 **Content-Type:** application/json  
-**Auth Required:** Yes (token)
+**Auth Required:** Yes (token)  
+**Permission Level:** Admin
 
 **Request Headers:**
 ```
@@ -208,7 +250,8 @@ X-Timestamp: 1704067200000
 **Endpoint:** `/frpcAct/instanceMgr/delete`  
 **Method:** POST  
 **Content-Type:** application/json  
-**Auth Required:** Yes (token)
+**Auth Required:** Yes (token)  
+**Permission Level:** Admin
 
 **Request Headers:**
 ```
@@ -241,7 +284,8 @@ X-Timestamp: 1704067200000
 **Endpoint:** `/frpcAct/instanceMgr/modify`  
 **Method:** POST  
 **Content-Type:** application/json  
-**Auth Required:** Yes (token)
+**Auth Required:** Yes (token)  
+**Permission Level:** Admin
 
 Modify instance configuration. Supports two modification types: `configFile` (modify frpc config file) and `systemConfig` (modify system-level settings).
 
@@ -365,7 +409,10 @@ Modify system-level settings such as instance name, boot-at-start configuration,
 
 **Endpoint:** `/frpcAct/instanceMgr/list`  
 **Method:** GET  
-**Auth Required:** Yes (token)
+**Auth Required:** Yes (token)  
+**Permission Level:** Admin
+
+Retrieve a list of all frpc instances.
 
 **Request Headers:**
 ```