feat: 新增账户服务层，实现账户的增删改查及转账功能，并初始化AI记账、交易服务和预算仓库。

internal/service/ai_bookkeeping_service.go

@@ -1407,9 +1407,71 @@ func (s *AIBookkeepingService) GenerateConfirmationCard(session *AISession) *Con
 		card.Date = time.Now().Format("2006-01-02")
 	}
 
+	// Check for budget warnings
+	if params.Amount != nil && *params.Amount > 0 && params.Type == "expense" {
+		card.Warning = s.checkBudgetWarning(session.UserID, params.CategoryID, *params.Amount)
+	}
+
 	return card
 }
 
+// checkBudgetWarning checks if the transaction exceeds any budget
+func (s *AIBookkeepingService) checkBudgetWarning(userID uint, categoryID *uint, amount float64) string {
+	now := time.Now()
+	var budgets []models.Budget
+
+	// Find active budgets
+	// We check:
+	// 1. Budgets specifically for this category
+	// 2. Global budgets (CategoryID is NULL)
+	query := s.db.Where("user_id = ?", userID).
+		Where("start_date <= ?", now).
+		Where("end_date IS NULL OR end_date >= ?", now)
+
+	if categoryID != nil {
+		query = query.Where("category_id = ? OR category_id IS NULL", *categoryID)
+	} else {
+		query = query.Where("category_id IS NULL")
+	}
+
+	if err := query.Find(&budgets).Error; err != nil {
+		return ""
+	}
+
+	for _, budget := range budgets {
+		// Calculate current period
+		start, end := s.calculateBudgetPeriod(&budget, now)
+
+		// Query spent amount
+		var totalSpent float64
+		q := s.db.Model(&models.Transaction{}).
+			Where("user_id = ? AND type = ? AND transaction_date BETWEEN ? AND ?",
+				userID, models.TransactionTypeExpense, start, end)
+
+		if budget.CategoryID != nil {
+			// Get sub-categories
+			var subCategoryIDs []uint
+			s.db.Model(&models.Category{}).Where("parent_id = ?", *budget.CategoryID).Pluck("id", &subCategoryIDs)
+			categoryIDs := append(subCategoryIDs, *budget.CategoryID)
+			q = q.Where("category_id IN ?", categoryIDs)
+		}
+		// If budget has account restriction, we should ideally check that too,
+		// but we don't always have accountID resolved here perfectly or it might be complex.
+		// For now, focusing on category budgets which are most common.
+
+		q.Select("COALESCE(SUM(amount), 0)").Scan(&totalSpent)
+
+		if totalSpent+amount > budget.Amount {
+			remaining := budget.Amount - totalSpent
+			if remaining < 0 {
+				remaining = 0
+			}
+			return fmt.Sprintf("⚠️ 预算预警：此交易将使【%s】预算超支 (当前剩余 %.2f)", budget.Name, remaining)
+		}
+	}
+	return ""
+}
+
 // TranscribeAudio transcribes audio and returns text
 func (s *AIBookkeepingService) TranscribeAudio(ctx context.Context, audioData io.Reader, filename string) (*TranscriptionResult, error) {
 	return s.whisperService.TranscribeAudio(ctx, audioData, filename)
@@ -1430,13 +1492,13 @@ func (s *AIBookkeepingService) ConfirmTransaction(ctx context.Context, sessionID
 
 	// Validate required fields
 	if params.Amount == nil || *params.Amount <= 0 {
-		return nil, errors.New("invalid amount")
+		return nil, errors.New("无效的金额")
 	}
 	if params.CategoryID == nil {
-		return nil, errors.New("category not specified")
+		return nil, errors.New("未指定分类")
 	}
 	if params.AccountID == nil {
-		return nil, errors.New("account not specified")
+		return nil, errors.New("未指定账户")
 	}
 
 	// Parse date
@@ -1480,7 +1542,7 @@ func (s *AIBookkeepingService) ConfirmTransaction(ctx context.Context, sessionID
 
 		// Critical Check: Prevent negative balance for non-credit accounts
 		if !account.IsCredit && newBalance < 0 {
-			return fmt.Errorf("insufficient balance: account '%s' does not support negative balance (current: %.2f, try: %.2f)",
+			return fmt.Errorf("余额不足：账户“%s”不支持负余额 (当前: %.2f, 尝试扣款: %.2f)",
 				account.Name, account.Balance, *params.Amount)
 		}