feat: 添加预算管理功能，包括预算的创建、查询、更新、删除及进度计算。

internal/models/models.go

@@ -278,6 +278,7 @@ type Account struct {
 	PiggyBanks            []PiggyBank            `gorm:"foreignKey:LinkedAccountID" json:"-"`
 	ParentAccount         *Account               `gorm:"foreignKey:ParentAccountID" json:"parent_account,omitempty"`
 	SubAccounts           []Account              `gorm:"foreignKey:ParentAccountID" json:"sub_accounts,omitempty"`
+	Tags                  []Tag                  `gorm:"many2many:account_tags;" json:"tags,omitempty"`
 }
 
 // TableName specifies the table name for Account
@@ -417,6 +418,17 @@ func (TransactionTag) TableName() string {
 	return "transaction_tags"
 }
 
+// AccountTag represents the many-to-many relationship between accounts and tags
+type AccountTag struct {
+	AccountID uint `gorm:"primaryKey" json:"account_id"`
+	TagID     uint `gorm:"primaryKey" json:"tag_id"`
+}
+
+// TableName specifies the table name for AccountTag
+func (AccountTag) TableName() string {
+	return "account_tags"
+}
+
 // Budget represents a spending budget for a category or account
 type Budget struct {
 	BaseModel
@@ -843,6 +855,7 @@ func AllModels() []interface{} {
 		&Tag{},
 		&Transaction{},
 		&TransactionTag{}, // Explicit join table for many-to-many relationship
+		&AccountTag{},     // Explicit join table for account-tag many-to-many relationship
 		&Budget{},
 		&PiggyBank{},
 		&RecurringTransaction{},