新增作文区与 AI 解读开关，修复 CSV 导出。

系统设置可关闭成绩复盘 AI；学生详情增加作文区（OCR/手动题目、方案与范文、历史与 MD 下载）；导出改用 UTF-8 文件名响应。

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

backend/app/routers/settings.py

@@ -2,8 +2,9 @@ from fastapi import APIRouter, Depends
 from sqlalchemy.orm import Session
 
 from app.core.database import get_db
-from app.models.user import SystemSettings
-from app.schemas import PublicSettingsOut
+from app.core.deps import get_current_user
+from app.models.user import SystemSettings, User
+from app.schemas import AppFeaturesOut, PublicSettingsOut
 
 router = APIRouter(prefix="/settings", tags=["settings"])
 
@@ -22,3 +23,12 @@ def get_or_create_settings(db: Session) -> SystemSettings:
 def public_settings(db: Session = Depends(get_db)):
     row = get_or_create_settings(db)
     return PublicSettingsOut(registration_enabled=row.registration_enabled)
+
+
+@router.get("/app-features", response_model=AppFeaturesOut)
+def app_features(
+    db: Session = Depends(get_db),
+    _: User = Depends(get_current_user),
+):
+    row = get_or_create_settings(db)
+    return AppFeaturesOut(ai_review_enabled=getattr(row, "ai_review_enabled", True))