feat(server-release): 出题批阅业务逻辑优化 — 移除20题限制、max_total支持、填空题格式校验、修正认证状态码

- exam_pkg/api.py: 移除总题数20道上限，改为50道警告；修正认证错误使用正确的UNAUTHORIZED/FORBIDDEN状态码；端点保持同步模式
- exam_pkg/generator.py: AI智能出题prompt支持max_total参数
- exam_pkg/grader.py: 填空题增加学生答案格式校验（列表类型+字符串元素）

exam_pkg/api.py

@@ -29,7 +29,7 @@ from auth.gateway import (
 )
 
 # 导入统一响应格式
-from core.status_codes import EXAM_SUCCESS, GRADE_SUCCESS, EXAM_ERROR, GRADE_ERROR, BAD_REQUEST, NO_CONTENT, LLM_ERROR
+from core.status_codes import EXAM_SUCCESS, GRADE_SUCCESS, EXAM_ERROR, GRADE_ERROR, BAD_REQUEST, UNAUTHORIZED, FORBIDDEN, NO_CONTENT, LLM_ERROR
 from api.response_utils import success_response, error_response
 
 # 合法题型
@@ -152,13 +152,14 @@ def api_generate_questions():
         if diff_error:
             return error_response("INVALID_PARAMS", BAD_REQUEST, diff_error, http_status=400)
 
-        # 校验总题数上限
-        MAX_TOTAL_QUESTIONS = 20
+        # 校验总题数（不设上限，但提醒用户大量出题可能影响性能）
         total_requested = sum(question_types.values())
-        if total_requested > MAX_TOTAL_QUESTIONS:
+        if total_requested <= 0:
             return error_response("INVALID_PARAMS", BAD_REQUEST,
-                f"总题数不能超过 {MAX_TOTAL_QUESTIONS} 道，当前请求 {total_requested} 道",
+                "总题数必须大于0",
                 http_status=400)
+        if total_requested > 50:
+            logger.warning(f"[出题] 请求生成 {total_requested} 道题，可能影响性能")
 
         # 校验排除题干列表（可选）
         exclude_stems = data.get('exclude_stems')
@@ -169,7 +170,7 @@ def api_generate_questions():
         # 获取当前用户
         user = get_current_user()
         if not user:
-            return error_response("UNAUTHORIZED", BAD_REQUEST, "未认证", http_status=401)
+            return error_response("UNAUTHORIZED", UNAUTHORIZED, "未认证", http_status=401)
 
         # 检查向量库访问权限
         if not check_collection_permission(
@@ -178,9 +179,9 @@ def api_generate_questions():
             collection_name=collection,
             operation="read"
         ):
-            return error_response("FORBIDDEN", BAD_REQUEST, "权限不足", http_status=403)
+            return error_response("FORBIDDEN", FORBIDDEN, "权限不足", http_status=403)
 
-        # 调用新版出题接口
+        # 调用新版出题接口（同步）
         result = generate_questions_from_file(
             file_path=file_path,
             collection=collection,
@@ -251,7 +252,7 @@ def api_generate_smart():
         # 获取当前用户
         user = get_current_user()
         if not user:
-            return error_response("UNAUTHORIZED", BAD_REQUEST, "未认证", http_status=401)
+            return error_response("UNAUTHORIZED", UNAUTHORIZED, "未认证", http_status=401)
 
         # 检查向量库访问权限
         if not check_collection_permission(
@@ -260,7 +261,7 @@ def api_generate_smart():
             collection_name=collection,
             operation="read"
         ):
-            return error_response("FORBIDDEN", BAD_REQUEST, "权限不足", http_status=403)
+            return error_response("FORBIDDEN", FORBIDDEN, "权限不足", http_status=403)
 
         # 1. 调用 AI 分析文件，获取推荐的题型和数量
         from exam_pkg.manager import analyze_file_for_exam