feat: 添加线索引擎、NLQ、场景检测、前端界面等核心功能模块

backend/app/llm/providers.py

@@ -78,3 +78,31 @@ class VllmProvider(LLMProvider):
                 return resp.status_code == 200
         except httpx.HTTPError:
             return False
+
+
+class MockProvider(LLMProvider):
+    """本地确定性 Mock Provider：开发/测试用，不出域、不依赖外网。
+
+    返回可预测的回显内容，便于在无 API Key / 无 GPU 时打通链路与自动化测试。
+    """
+
+    name = "mock"
+    egress = False
+
+    def __init__(self, model: str = "mock-llm") -> None:
+        self._model = model
+
+    def chat(self, messages: list[ChatMessage], **kwargs) -> LLMResponse:
+        last_user = next(
+            (m.content for m in reversed(messages) if m.role == "user"), ""
+        )
+        return LLMResponse(
+            content=f"[mock] 收到查询：{last_user}",
+            model=self._model,
+            provider=self.name,
+            egress=False,
+            raw={"echo": last_user},
+        )
+
+    def health(self) -> bool:
+        return True