Add FastAPI backend with agent system

backend/app/schemas/graph.py

@@ -0,0 +1,66 @@
+from pydantic import BaseModel, Field
+from typing import Literal
+
+
+class TagProperties(BaseModel):
+    tag_path: str = Field(..., description="完整标签路径，如 '编程语言/Python/异步'")
+    short_name: str = Field(..., description="显示名称，如 '异步'")
+    level: int = Field(..., ge=1, description="层级深度，1为顶级")
+    parent_path: str | None = Field(None, description="父路径，如 '编程语言/Python'")
+    description: str | None = Field(None, description="AI生成的标签描述")
+    color: str | None = Field(None, description="标签颜色，如 '#FF5733'")
+
+
+class KGNodeOut(BaseModel):
+    id: str
+    name: str
+    entity_type: str
+    description: str | None
+    properties_: dict | None
+    importance: float
+    created_at: str
+    # 新增：如果是 tag 节点，返回 tag 属性
+    tag_properties: TagProperties | None = None
+
+    model_config = {"from_attributes": True}
+
+    def model_post_init(self, __context):
+        if self.entity_type == "tag" and self.properties_:
+            self.tag_properties = TagProperties(**self.properties_)
+
+
+class KGEdgeOut(BaseModel):
+    id: str
+    source_id: str
+    target_id: str
+    relation_type: str
+    weight: float
+    properties_: dict | None
+
+    model_config = {"from_attributes": True}
+
+
+class GraphOut(BaseModel):
+    nodes: list[KGNodeOut]
+    edges: list[KGEdgeOut]
+
+
+class KGBuildRequest(BaseModel):
+    user_id: str
+    document_ids: list[str] | None = None  # None = 全量重建
+
+
+class TagExtractRequest(BaseModel):
+    content: str = Field(..., min_length=10)
+    user_id: str
+
+
+class TagExtractResponse(BaseModel):
+    tags: list[TagProperties]
+    tag_count: int
+
+
+class RelatedContentRequest(BaseModel):
+    tag_ids: list[str]
+    user_id: str
+    limit: int = 10