feat: 新增预算后端服务与差旅风险规则库

后端新增预算模型、端点和服务模块，支持预算 CRUD 和余额
查询，清理旧生成规则文件并替换为按严重等级分类的差旅风
险规则库，优化认证权限和报销单访问策略，新增财务规则目
录和演示数据构建脚本，前端预算中心增加对话框交互，完善
审计页面运行时模型和元数据展示，补充单元测试。

server/src/app/services/risk_rule_template_executor.py

@@ -519,6 +519,8 @@ class RiskRuleTemplateExecutor:
             )
         if normalized.startswith("attachment."):
             return self._resolve_attachment_values(normalized.removeprefix("attachment."), contexts)
+        if normalized.startswith("budget."):
+            return self._resolve_budget_values(normalized.removeprefix("budget."), contexts)
         return []
 
     @staticmethod
@@ -566,6 +568,19 @@ class RiskRuleTemplateExecutor:
                 values.extend(self._scan_document_values(document_info, field_key))
         return self._normalize_values(values)
 
+    def _resolve_budget_values(self, field_key: str, contexts: list[dict[str, Any]]) -> list[str]:
+        values: list[Any] = []
+        for context in contexts:
+            if not isinstance(context, dict):
+                continue
+            budget_context = context.get("budget_context")
+            if not isinstance(budget_context, dict):
+                continue
+            for key in {field_key, field_key.replace("_", ""), field_key.replace("-", "_")}:
+                if key in budget_context:
+                    values.append(budget_context.get(key))
+        return self._normalize_values(values)
+
     def _scan_document_values(self, document_info: dict[str, Any], field_key: str) -> list[Any]:
         values: list[Any] = []
         for key in {field_key, field_key.replace("_", ""), field_key.replace("_", "-")}: