Initial commit: QMDSearch 分层信息检索服务

- FastAPI + Qdrant + Redis + Ollama 技术栈
- L1→L2→L3→chunk 四层分层检索（dense + sparse RRF 融合）
- 文档三级总结与 2.5 级回退
- query 解析路由与分类
- /admin 管理页面

app/main.py

@@ -0,0 +1,79 @@
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+from pathlib import Path
+
+import structlog
+from fastapi import FastAPI, Request
+from fastapi.exceptions import RequestValidationError
+from fastapi.responses import FileResponse, JSONResponse
+
+from app.api.response import ApiError, error
+from app.api.v1.document import router as document_router
+from app.api.v1.knowledge import router as knowledge_router
+from app.api.v1.search import router as search_router
+from app.config import settings
+from app.services.qdrant import QdrantService
+
+logger = structlog.get_logger()
+
+
+@asynccontextmanager
+async def lifespan(_: FastAPI) -> AsyncIterator[None]:
+    """应用生命周期：启动时初始化 Qdrant 集合
+
+    初始化失败仅记录日志、不阻止启动（本地开发可能无 Qdrant）。
+    """
+    try:
+        await QdrantService().ensure_collections()
+        logger.info("Qdrant 集合初始化完成")
+    except Exception:
+        logger.error("Qdrant 集合初始化失败，跳过初始化继续启动")
+    yield
+
+
+app = FastAPI(
+    title=settings.app_name,
+    description="AI Agent 分层信息检索服务",
+    version="0.1.0",
+    lifespan=lifespan,
+)
+
+app.include_router(search_router)
+app.include_router(document_router)
+app.include_router(knowledge_router)
+
+
+@app.exception_handler(ApiError)
+async def api_error_handler(request: Request, exc: ApiError) -> JSONResponse:
+    """业务异常 → 统一错误响应（code 取自异常）"""
+    return JSONResponse(content=error(exc.code, exc.message))
+
+
+@app.exception_handler(RequestValidationError)
+async def validation_error_handler(request: Request, exc: RequestValidationError) -> JSONResponse:
+    """请求参数校验失败 → code 1001"""
+    errors = exc.errors()
+    message = f"请求参数校验失败: {errors[0]['msg']}" if errors else "请求参数校验失败"
+    return JSONResponse(content=error(1001, message))
+
+
+@app.exception_handler(Exception)
+async def unhandled_error_handler(request: Request, exc: Exception) -> JSONResponse:
+    """未捕获异常 → code 2000"""
+    logger.exception("未捕获异常", path=request.url.path)
+    return JSONResponse(content=error(2000, "服务器内部错误"))
+
+
+@app.get("/api/v1/health")
+async def health() -> dict[str, str]:
+    """健康检查"""
+    return {"status": "ok"}
+
+
+_ADMIN_HTML = Path(__file__).resolve().parent / "static" / "admin.html"
+
+
+@app.get("/admin", include_in_schema=False)
+async def admin_page() -> FileResponse:
+    """管理后台单页（单文件静态 HTML，零外部依赖）"""
+    return FileResponse(_ADMIN_HTML, media_type="text/html")