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。

web/src/assets/styles/views/budget-center-dialog.css

@@ -63,11 +63,24 @@
 .budget-edit-body {
   min-height: 0;
   padding: 18px 24px 16px;
-  overflow: auto;
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
+}
+
+.budget-edit-section {
+  display: flex;
+  flex-direction: column;
+  min-height: 0;
+}
+
+.budget-edit-section:first-child {
+  flex-shrink: 0;
 }
 
 .budget-edit-section + .budget-edit-section {
   margin-top: 18px;
+  flex: 1;
 }
 
 .budget-edit-section h3 {
@@ -76,6 +89,7 @@
   font-size: 15px;
   line-height: 1.35;
   font-weight: 800;
+  flex-shrink: 0;
 }
 
 .budget-edit-form-grid {
@@ -153,6 +167,9 @@
   border: 1px solid #edf1f6;
   border-radius: 8px;
   overflow-x: auto;
+  overflow-y: auto;
+  flex: 1;
+  min-height: 0;
 }
 
 .budget-edit-table {
@@ -243,27 +260,35 @@
   font-size: 13px;
   font-weight: 800;
   cursor: pointer;
+  flex-shrink: 0;
 }
 
 .budget-edit-total {
   height: 42px;
   margin-top: 8px;
   padding: 0 14px;
-  display: grid;
-  grid-template-columns: 120px 1fr;
+  display: flex;
+  justify-content: flex-end;
+  gap: 12px;
   align-items: center;
   border: 1px solid #edf1f6;
   border-radius: 8px;
   background: #fbfcfe;
+  flex-shrink: 0;
 }
 
-.budget-edit-total span,
-.budget-edit-total strong {
+.budget-edit-total span {
   color: #111827;
   font-size: 14px;
   font-weight: 800;
 }
 
+.budget-edit-total strong {
+  color: #059669;
+  font-size: 16px;
+  font-weight: 800;
+}
+
 .budget-edit-foot {
   padding: 18px 24px 20px;
   display: flex;

web/src/assets/styles/views/budget-center-view.css

@@ -252,6 +252,10 @@
   gap: 10px;
 }
 
+.budget-work-grid.single-department {
+  grid-template-columns: minmax(0, 1fr);
+}
+
 .budget-department-panel,
 .budget-table-panel,
 .budget-chart-panel,