feat: 增强风险规则生成引擎与预算中心页面

后端拆分风险规则生成为解释器、语义分析、本体对齐等子模块，
优化模板执行和流程图生成，完善员工种子数据和导入逻辑，增强
报销单权限策略和草稿持久化，前端新增预算中心视图和趋势图
组件，重构审计页面和风险规则测试对话框交互，完善文档中心
和报销创建页面细节，补充单元测试覆盖。

server/src/app/schemas/agent_asset.py

@@ -113,7 +113,8 @@ class AgentAssetRuleJsonRead(BaseModel):
 class AgentAssetRiskRuleGenerateRequest(BaseModel):
     business_domain: AgentAssetDomain = AgentAssetDomain.EXPENSE
     expense_category: str | None = Field(default=None, max_length=40)
-    risk_level: str = Field(default="medium", pattern="^(low|medium|high)$")
+    rule_title: str | None = Field(default=None, max_length=80)
+    risk_level: str | None = Field(default=None, pattern="^(low|medium|high|critical)$")
     natural_language: str = Field(min_length=8, max_length=2000)
     requires_attachment: bool = False
 
@@ -195,6 +196,10 @@ class AgentAssetRiskRuleEnabledUpdate(BaseModel):
     enabled: bool
 
 
+class AgentAssetRiskRuleLevelUpdate(BaseModel):
+    risk_level: str = Field(pattern="^(low|medium|high|critical)$")
+
+
 class AgentAssetRiskRuleTestRunRead(BaseModel):
     model_config = ConfigDict(from_attributes=True)