移动端拍照上传、奥数区、学段约束解题与 AI 模型配置。

- 手机/平板响应式布局，支持拍照与相册上传

- 学生详情新增奥数区，按初/高中学段生成解法并禁止超纲

- 系统设置可配置 Ollama 或 OpenAI 兼容 API

- 更新 frontend/dist 与使用说明

backend/app/routers/admin.py

@@ -13,6 +13,7 @@ from app.schemas import (
     AdminUserCreate,
     AdminUserOut,
     AdminUserPasswordUpdate,
+    AIProviderEnum,
     PublicSettingsOut,
     SystemSettingsOut,
     SystemSettingsUpdate,
@@ -21,6 +22,19 @@ from app.schemas import (
 router = APIRouter(prefix="/admin", tags=["admin"])
 
 
+def settings_to_out(row: SystemSettings) -> SystemSettingsOut:
+    return SystemSettingsOut(
+        registration_enabled=row.registration_enabled,
+        ai_provider=AIProviderEnum(row.ai_provider or "ollama"),
+        ollama_base_url=row.ollama_base_url,
+        ollama_model=row.ollama_model,
+        openai_base_url=row.openai_base_url,
+        openai_model=row.openai_model,
+        openai_api_key_set=bool(row.openai_api_key),
+        updated_at=row.updated_at,
+    )
+
+
 def get_or_create_settings(db: Session) -> SystemSettings:
     row = db.get(SystemSettings, 1)
     if row is None:
@@ -36,7 +50,7 @@ def get_settings(
     db: Session = Depends(get_db),
     _: User = Depends(get_superuser),
 ):
-    return get_or_create_settings(db)
+    return settings_to_out(get_or_create_settings(db))
 
 
 @router.patch("/settings", response_model=SystemSettingsOut)
@@ -48,10 +62,22 @@ def update_settings(
     row = get_or_create_settings(db)
     if data.registration_enabled is not None:
         row.registration_enabled = data.registration_enabled
+    if data.ai_provider is not None:
+        row.ai_provider = data.ai_provider.value
+    if data.ollama_base_url is not None:
+        row.ollama_base_url = data.ollama_base_url or None
+    if data.ollama_model is not None:
+        row.ollama_model = data.ollama_model or None
+    if data.openai_base_url is not None:
+        row.openai_base_url = data.openai_base_url or None
+    if data.openai_model is not None:
+        row.openai_model = data.openai_model or None
+    if data.openai_api_key is not None and data.openai_api_key.strip():
+        row.openai_api_key = data.openai_api_key.strip()
     row.updated_at = datetime.now(timezone.utc)
     db.commit()
     db.refresh(row)
-    return row
+    return settings_to_out(row)
 
 
 @router.patch("/profile", response_model=AdminUserOut)