feat: add ChromaDB database layer

src/core/db.py

@@ -0,0 +1,25 @@
+"""ChromaDB 数据库层."""
+import chromadb
+from chromadb.api.models.Collection import Collection
+
+
+class VectorDB:
+    """向量数据库封装."""
+
+    def __init__(self, persist_dir: str = "./data"):
+        self.client = chromadb.PersistentClient(path=persist_dir)
+
+    def get_or_create_collection(self, name: str) -> Collection:
+        """获取或创建 collection."""
+        return self.client.get_or_create_collection(name=name)
+
+    def delete_collection(self, name: str) -> None:
+        """删除 collection."""
+        try:
+            self.client.delete_collection(name=name)
+        except ValueError:
+            pass  # collection 不存在则忽略
+
+    def close(self) -> None:
+        """释放数据库连接."""
+        self.client.close()