feat: 新增风险规则生成引擎与知识图谱可视化

后端新增风险规则自动生成和模板执行服务，支持从规则资产
批量生成并持久化风险规则文件；知识库入库日志增强图谱
查询和本地 RAG 回退，前端审计页面增加风险规则模型和流
程图组件，知识入库面板拆分为图谱可视化子组件，报销创
建页面增加引导式流程模型，更新知识库索引数据。

server/src/app/schemas/agent_asset.py

@@ -104,11 +104,18 @@ class AgentAssetRuleJsonRead(BaseModel):
     description: str = ""
     evaluator: str = ""
     ontology_signal: str | None = None
+    flow_diagram_svg: str | None = None
     inputs: dict[str, Any] = Field(default_factory=dict)
     outcomes: dict[str, Any] = Field(default_factory=dict)
     payload: dict[str, Any] = Field(default_factory=dict)
 
 
+class AgentAssetRiskRuleGenerateRequest(BaseModel):
+    business_domain: AgentAssetDomain = AgentAssetDomain.EXPENSE
+    risk_level: str = Field(default="medium", pattern="^(low|medium|high)$")
+    natural_language: str = Field(min_length=8, max_length=2000)
+
+
 class AgentAssetVersionTimelineItemRead(BaseModel):
     event_type: str
     version: str