feat: 完善预算中心图表与确认对话框交互

后端预算服务增加汇总查询和辅助计算，前端预算中心优化趋
势图组件和数据展示，增强确认对话框通用性和样式，完善预
算编辑对话框布局，补充预算端点单元测试。

server/src/app/services/budget.py

@@ -92,6 +92,7 @@ class BudgetService(BudgetSupportMixin):
         over_budget_count = sum(
             1 for item in allocations if item.balance.available_amount < Decimal("0.00")
         )
+        warnings = self.build_summary_warnings(allocations)
         return BudgetSummaryRead(
             fiscal_year=fiscal_year,
             period_key=period_key,
@@ -102,6 +103,13 @@ class BudgetService(BudgetSupportMixin):
             warning_count=warning_count,
             over_budget_count=over_budget_count,
             allocations=allocations,
+            trend=self.build_summary_trend(
+                fiscal_year=fiscal_year,
+                department_id=department_id,
+                department_name=department_name,
+                cost_center=cost_center,
+            ),
+            warnings=warnings,
         )
 
     def create_or_update_allocation(