feat: 实现前端卡密管理界面

- 卡密列表展示与分页功能

- 单个/批量创建卡密

- 卡密删除与批量删除

- 卡密导出功能 (file-saver)

- 启用/禁用状态切换

- 状态判断 (有效/已使用/已失效)

- Toast 通知系统 (vue-sonner)

- 登录页面错误提示优化

- 后端登录错误消息中文化

backend/internal/repository/invitation_repo.go

@@ -0,0 +1,109 @@
+package repository
+
+import (
+	"database/sql"
+	"time"
+
+	"gpt-manager-go/internal/models"
+)
+
+// InvitationRepository 邀请记录仓储
+type InvitationRepository struct {
+	db *sql.DB
+}
+
+// NewInvitationRepository 创建仓储
+func NewInvitationRepository(db *sql.DB) *InvitationRepository {
+	return &InvitationRepository{db: db}
+}
+
+// Create 创建邀请记录
+func (r *InvitationRepository) Create(invitation *models.Invitation) error {
+	return r.db.QueryRow(`
+		INSERT INTO invitations (card_key_id, account_id, invited_email, status, error_message, expires_at, created_at)
+		VALUES ($1, $2, $3, $4, $5, $6, $7)
+		RETURNING id
+	`,
+		invitation.CardKeyID,
+		invitation.AccountID,
+		invitation.InvitedEmail,
+		invitation.Status,
+		invitation.ErrorMessage,
+		invitation.ExpiresAt,
+		time.Now(),
+	).Scan(&invitation.ID)
+}
+
+// FindByEmail 根据邮箱查找邀请记录
+func (r *InvitationRepository) FindByEmail(email string) ([]*models.Invitation, error) {
+	rows, err := r.db.Query(`
+		SELECT id, card_key_id, account_id, invited_email, status, error_message, expires_at, created_at, updated_at
+		FROM invitations WHERE invited_email = $1 ORDER BY created_at DESC
+	`, email)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var invitations []*models.Invitation
+	for rows.Next() {
+		inv := &models.Invitation{}
+		if err := rows.Scan(
+			&inv.ID, &inv.CardKeyID, &inv.AccountID, &inv.InvitedEmail,
+			&inv.Status, &inv.ErrorMessage, &inv.ExpiresAt,
+			&inv.CreatedAt, &inv.UpdatedAt,
+		); err != nil {
+			return nil, err
+		}
+		invitations = append(invitations, inv)
+	}
+	return invitations, nil
+}
+
+// UpdateStatus 更新邀请状态
+func (r *InvitationRepository) UpdateStatus(id int, status models.InvitationStatus, errMsg string) error {
+	var errMsgSQL sql.NullString
+	if errMsg != "" {
+		errMsgSQL = sql.NullString{String: errMsg, Valid: true}
+	}
+
+	_, err := r.db.Exec(`
+		UPDATE invitations SET status = $1, error_message = $2, updated_at = $3
+		WHERE id = $4
+	`, status, errMsgSQL, time.Now(), id)
+	return err
+}
+
+// DeleteByEmailAndAccountID 根据邮箱和账号ID删除邀请记录
+func (r *InvitationRepository) DeleteByEmailAndAccountID(email string, accountID int) error {
+	_, err := r.db.Exec(`
+		DELETE FROM invitations WHERE invited_email = $1 AND account_id = $2
+	`, email, accountID)
+	return err
+}
+
+// FindByAccountID 根据账号ID查找邀请记录
+func (r *InvitationRepository) FindByAccountID(accountID int) ([]*models.Invitation, error) {
+	rows, err := r.db.Query(`
+		SELECT id, card_key_id, account_id, invited_email, status, error_message, expires_at, created_at, updated_at
+		FROM invitations WHERE account_id = $1 ORDER BY created_at DESC
+	`, accountID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var invitations []*models.Invitation
+	for rows.Next() {
+		inv := &models.Invitation{}
+		if err := rows.Scan(
+			&inv.ID, &inv.CardKeyID, &inv.AccountID, &inv.InvitedEmail,
+			&inv.Status, &inv.ErrorMessage, &inv.ExpiresAt,
+			&inv.CreatedAt, &inv.UpdatedAt,
+		); err != nil {
+			return nil, err
+		}
+		invitations = append(invitations, inv)
+	}
+	return invitations, nil
+}