feat: 添加预算服务，包含预算的增删改查、进度获取及相关工具函数

src/services/budgetService.ts

@@ -5,6 +5,47 @@
 import api from './api';
 import type { Budget, ApiResponse, BudgetPeriodType } from '../types';
 
+/**
+ * Backend Budget API response (snake_case)
+ */
+interface ApiBudget {
+  id: number;
+  name: string;
+  amount: number;
+  period_type: BudgetPeriodType;
+  category_id?: number;
+  account_id?: number;
+  is_rolling: boolean;
+  start_date: string;
+  end_date?: string;
+  spent?: number;
+  progress?: number;
+  created_at: string;
+  // Nested objects from Preload
+  category?: { id: number; name: string; icon?: string };
+  account?: { id: number; name: string };
+}
+
+/**
+ * Convert backend API response to frontend Budget model
+ */
+function mapApiBudgetToBudget(apiBudget: ApiBudget): Budget {
+  return {
+    id: apiBudget.id,
+    name: apiBudget.name,
+    amount: apiBudget.amount,
+    periodType: apiBudget.period_type,
+    categoryId: apiBudget.category_id,
+    accountId: apiBudget.account_id,
+    isRolling: apiBudget.is_rolling,
+    startDate: apiBudget.start_date,
+    endDate: apiBudget.end_date,
+    spent: apiBudget.spent ?? 0,
+    progress: apiBudget.progress ?? 0,
+    createdAt: apiBudget.created_at,
+  };
+}
+
 /**
  * Budget form input interface
  */
@@ -35,19 +76,20 @@ export interface BudgetProgress {
  * Get all budgets
  */
 export async function getBudgets(): Promise<Budget[]> {
-  const response = await api.get<ApiResponse<Budget[]>>('/budgets');
+  const response = await api.get<ApiResponse<ApiBudget[]>>('/budgets');
-  return response.data || [];
+  const apiBudgets = response.data || [];
+  return apiBudgets.map(mapApiBudgetToBudget);
 }
 
 /**
  * Get a single budget by ID
  */
 export async function getBudget(id: number): Promise<Budget> {
-  const response = await api.get<ApiResponse<Budget>>(`/budgets/${id}`);
+  const response = await api.get<ApiResponse<ApiBudget>>(`/budgets/${id}`);
   if (!response.data) {
     throw new Error('Budget not found');
   }
-  return response.data;
+  return mapApiBudgetToBudget(response.data);
 }
 
 /**
@@ -77,11 +119,11 @@ export async function createBudget(data: BudgetFormInput): Promise<Budget> {
     start_date: data.startDate ? `${data.startDate}T00:00:00Z` : undefined,
     end_date: data.endDate ? `${data.endDate}T23:59:59Z` : undefined,
   };
-  const response = await api.post<ApiResponse<Budget>>('/budgets', payload);
+  const response = await api.post<ApiResponse<ApiBudget>>('/budgets', payload);
   if (!response.data) {
     throw new Error(response.error || 'Failed to create budget');
   }
-  return response.data;
+  return mapApiBudgetToBudget(response.data);
 }
 
 /**
@@ -100,11 +142,11 @@ export async function updateBudget(id: number, data: Partial<BudgetFormInput>):
   if (data.startDate !== undefined) payload.start_date = `${data.startDate}T00:00:00Z`;
   if (data.endDate !== undefined) payload.end_date = data.endDate ? `${data.endDate}T23:59:59Z` : null;
 
-  const response = await api.put<ApiResponse<Budget>>(`/budgets/${id}`, payload);
+  const response = await api.put<ApiResponse<ApiBudget>>(`/budgets/${id}`, payload);
   if (!response.data) {
     throw new Error(response.error || 'Failed to update budget');
   }
-  return response.data;
+  return mapApiBudgetToBudget(response.data);
 }
 
 /**