Add FastAPI backend with agent system

backend/app/models/document.py

@@ -0,0 +1,33 @@
+from sqlalchemy import Column, String, Integer, Text, ForeignKey, Boolean
+from sqlalchemy.orm import relationship
+from app.models.base import BaseModel
+
+
+class Document(BaseModel):
+    __tablename__ = "documents"
+
+    user_id = Column(String(36), ForeignKey("users.id"), nullable=False, index=True)
+    title = Column(String(500), nullable=False)
+    filename = Column(String(500), nullable=False)
+    file_type = Column(String(50), nullable=False)  # pdf, md, txt, docx
+    file_size = Column(Integer, nullable=False)
+    file_path = Column(String(1000), nullable=False)
+    folder_id = Column(String(36), ForeignKey("folders.id"), nullable=True)  # 新增
+    summary = Column(Text, nullable=True)
+    chunk_count = Column(Integer, default=0)
+    is_indexed = Column(Boolean, default=False)
+
+    chunks = relationship("DocumentChunk", back_populates="document", cascade="all, delete-orphan")
+
+
+class DocumentChunk(BaseModel):
+    __tablename__ = "document_chunks"
+
+    document_id = Column(String(36), ForeignKey("documents.id"), nullable=False, index=True)
+    chunk_index = Column(Integer, nullable=False)
+    content = Column(Text, nullable=False)
+    metadata_ = Column(String(2000), nullable=True)  # JSON 存储元数据
+    chroma_collection = Column(String(255), nullable=True)
+    chroma_id = Column(String(255), nullable=True)
+
+    document = relationship("Document", back_populates="chunks")