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/schemas/budget.py

@@ -92,6 +92,37 @@ class BudgetTransactionRead(BaseModel):
     created_at: datetime
 
 
+class BudgetTrendPointRead(BaseModel):
+    period_key: str
+    label: str
+    total_amount: Decimal
+    reserved_amount: Decimal
+    consumed_amount: Decimal
+    used_amount: Decimal
+    available_amount: Decimal
+    usage_rate: Decimal
+
+
+class BudgetWarningRead(BaseModel):
+    allocation_id: str
+    budget_no: str
+    fiscal_year: int
+    period_key: str
+    department_name: str
+    cost_center: str | None = None
+    subject_code: str
+    subject_name: str
+    total_amount: Decimal
+    reserved_amount: Decimal
+    consumed_amount: Decimal
+    available_amount: Decimal
+    usage_rate: Decimal
+    warning_threshold: Decimal
+    severity: str
+    message: str
+    occurred_at: datetime | None = None
+
+
 class BudgetSummaryRead(BaseModel):
     fiscal_year: int | None = None
     period_key: str | None = None
@@ -102,6 +133,8 @@ class BudgetSummaryRead(BaseModel):
     warning_count: int
     over_budget_count: int
     allocations: list[BudgetAllocationRead] = Field(default_factory=list)
+    trend: list[BudgetTrendPointRead] = Field(default_factory=list)
+    warnings: list[BudgetWarningRead] = Field(default_factory=list)
 
 
 class BudgetCheckRead(BaseModel):