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/api/v1/knowledge.py

@@ -0,0 +1,75 @@
+"""知识分类 API：GET /api/v1/knowledge/categories、GET /api/v1/knowledge/stats"""
+
+from functools import lru_cache
+from typing import Any
+
+import structlog
+from fastapi import APIRouter
+
+from app.api.response import ApiError, ok
+from app.config import settings
+from app.models.knowledge import UNCATEGORIZED, TaxonomyCategory, load_taxonomy
+from app.services.qdrant import ALL_COLLECTIONS, COLLECTION_L1, QdrantService
+
+logger = structlog.get_logger()
+
+router = APIRouter(prefix="/api/v1", tags=["knowledge"])
+
+# 类目分布统计的分页大小
+_STATS_SCROLL_PAGE_SIZE = 100
+
+# 模块级懒加载单例，避免每请求重建 QdrantService
+_qdrant: QdrantService | None = None
+
+
+def _get_qdrant() -> QdrantService:
+    global _qdrant
+    if _qdrant is None:
+        _qdrant = QdrantService()
+    return _qdrant
+
+
+@lru_cache(maxsize=1)
+def _get_taxonomy() -> list[TaxonomyCategory]:
+    """加载并缓存 taxonomy 类目集（进程内只加载一次）"""
+    return load_taxonomy(settings.taxonomy_path)
+
+
+@router.get("/knowledge/categories")
+async def list_categories() -> dict[str, Any]:
+    """返回完整知识分类类目集"""
+    categories = _get_taxonomy()
+    return ok({"categories": [c.model_dump() for c in categories], "count": len(categories)})
+
+
+@router.get("/knowledge/stats")
+async def knowledge_stats() -> dict[str, Any]:
+    """返回四层集合规模与 L1 类目分布统计"""
+    service = _get_qdrant()
+    try:
+        collections = {collection: await service.count(collection) for collection in ALL_COLLECTIONS}
+        categories = await _aggregate_l1_categories(service)
+    except Exception as exc:
+        logger.error("获取知识库统计失败", error=str(exc))
+        raise ApiError(2000, f"获取知识库统计失败: {exc}") from exc
+    return ok(
+        {
+            "collections": collections,
+            "categories": categories,
+            "uncategorized_count": categories.get(UNCATEGORIZED, 0),
+            "documents_total": collections[COLLECTION_L1],
+        }
+    )
+
+
+async def _aggregate_l1_categories(service: QdrantService) -> dict[str, int]:
+    """分页遍历 L1 文档，按 category 聚合文档数（空类目归入 uncategorized）"""
+    categories: dict[str, int] = {}
+    offset: str | None = None
+    while True:
+        items, offset = await service.scroll_l1(limit=_STATS_SCROLL_PAGE_SIZE, offset=offset)
+        for item in items:
+            category = item.get("category") or UNCATEGORIZED
+            categories[category] = categories.get(category, 0) + 1
+        if offset is None:
+            return categories