feat: 添加预算管理功能，包括其handler、service和repository层。

internal/handler/budget_handler.go

@@ -98,6 +98,7 @@ func (h *BudgetHandler) GetBudget(c *gin.Context) {
 }
 
 // GetAllBudgets handles GET /api/v1/budgets
+// Returns budgets with calculated spent and progress fields
 func (h *BudgetHandler) GetAllBudgets(c *gin.Context) {
 	// Get user ID from context
 	userID, exists := c.Get("user_id")
@@ -106,7 +107,8 @@ func (h *BudgetHandler) GetAllBudgets(c *gin.Context) {
 		return
 	}
 
-	budgets, err := h.service.GetAllBudgets(userID.(uint))
+	// Use GetAllBudgetsWithProgress to return budgets with spent and progress calculated
+	budgets, err := h.service.GetAllBudgetsWithProgress(userID.(uint))
 	if err != nil {
 		api.InternalError(c, "Failed to get budgets")
 		return

internal/repository/budget_repository.go

@@ -66,8 +66,19 @@ func (r *BudgetRepository) Update(budget *models.Budget) error {
 		return fmt.Errorf("failed to check budget existence: %w", err)
 	}
 
-	// Update the budget
-	if err := r.db.Save(budget).Error; err != nil {
+	// Update the budget using Select to explicitly specify fields to update
+	// This ensures that nil/NULL values for CategoryID and AccountID are properly saved
+	if err := r.db.Model(budget).Select(
+		"name",
+		"amount",
+		"period_type",
+		"category_id", // Explicitly include to allow setting to NULL
+		"account_id",  // Explicitly include to allow setting to NULL
+		"is_rolling",
+		"start_date",
+		"end_date",
+		"updated_at",
+	).Updates(budget).Error; err != nil {
 		return fmt.Errorf("failed to update budget: %w", err)
 	}
 	return nil

internal/service/budget_service.go

@@ -126,6 +126,65 @@ func (s *BudgetService) GetAllBudgets(userID uint) ([]models.Budget, error) {
 	return budgets, nil
 }
 
+// BudgetWithProgress represents a budget with calculated progress fields
+type BudgetWithProgress struct {
+	models.Budget
+	Spent    float64 `json:"spent"`
+	Progress float64 `json:"progress"`
+}
+
+// GetAllBudgetsWithProgress retrieves all budgets with calculated spent and progress for a user
+func (s *BudgetService) GetAllBudgetsWithProgress(userID uint) ([]BudgetWithProgress, error) {
+	budgets, err := s.repo.GetAll(userID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get budgets: %w", err)
+	}
+
+	result := make([]BudgetWithProgress, len(budgets))
+	now := time.Now()
+
+	for i, budget := range budgets {
+		// Calculate current period
+		startDate, endDate := s.calculateCurrentPeriod(&budget, now)
+
+		// Get spent amount for current period
+		spent, err := s.repo.GetSpentAmount(&budget, startDate, endDate)
+		if err != nil {
+			// Log error but continue with 0 spent
+			spent = 0
+		}
+
+		// Calculate effective amount and progress
+		effectiveAmount := budget.Amount
+
+		if budget.IsRolling {
+			// For rolling budgets, calculate effective amount
+			periodsElapsed := s.calculatePeriodsElapsed(&budget, startDate)
+			totalBudget := budget.Amount * float64(periodsElapsed+1)
+
+			historyEnd := startDate.Add(-time.Second)
+			historySpent := 0.0
+			if historyEnd.After(budget.StartDate) {
+				historySpent, _ = s.repo.GetSpentAmount(&budget, budget.StartDate, historyEnd)
+			}
+			effectiveAmount = totalBudget - historySpent
+		}
+
+		progress := 0.0
+		if effectiveAmount > 0 {
+			progress = (spent / effectiveAmount) * 100
+		}
+
+		result[i] = BudgetWithProgress{
+			Budget:   budget,
+			Spent:    spent,
+			Progress: progress,
+		}
+	}
+
+	return result, nil
+}
+
 // UpdateBudget updates an existing budget after verifying ownership
 func (s *BudgetService) UpdateBudget(userID, id uint, input BudgetInput) (*models.Budget, error) {
 	// Get existing budget