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/card_key_repo.go

@@ -0,0 +1,149 @@
+package repository
+
+import (
+	"database/sql"
+
+	"gpt-manager-go/internal/models"
+
+	"github.com/lib/pq"
+)
+
+// CardKeyRepository 卡密仓储
+type CardKeyRepository struct {
+	db *sql.DB
+}
+
+// NewCardKeyRepository 创建仓储
+func NewCardKeyRepository(db *sql.DB) *CardKeyRepository {
+	return &CardKeyRepository{db: db}
+}
+
+// FindByKey 根据卡密查找
+func (r *CardKeyRepository) FindByKey(key string) (*models.CardKey, error) {
+	cardKey := &models.CardKey{}
+	err := r.db.QueryRow(`
+		SELECT id, key, max_uses, used_count, validity_type, expires_at, is_active, created_by_id, created_at
+		FROM card_keys WHERE key = $1
+	`, key).Scan(
+		&cardKey.ID, &cardKey.Key, &cardKey.MaxUses, &cardKey.UsedCount,
+		&cardKey.ValidityType, &cardKey.ExpiresAt, &cardKey.IsActive,
+		&cardKey.CreatedByID, &cardKey.CreatedAt,
+	)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	return cardKey, err
+}
+
+// IncrementUsedCount 增加使用次数，如果达到最大次数则设为不活跃
+func (r *CardKeyRepository) IncrementUsedCount(id int) error {
+	_, err := r.db.Exec(`
+		UPDATE card_keys 
+		SET used_count = used_count + 1,
+		    is_active = CASE WHEN used_count + 1 >= max_uses THEN false ELSE is_active END
+		WHERE id = $1
+	`, id)
+	return err
+}
+
+// Create 创建卡密
+func (r *CardKeyRepository) Create(cardKey *models.CardKey) error {
+	return r.db.QueryRow(`
+		INSERT INTO card_keys (key, max_uses, used_count, validity_type, expires_at, is_active, created_by_id, created_at)
+		VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
+		RETURNING id
+	`,
+		cardKey.Key,
+		cardKey.MaxUses,
+		cardKey.UsedCount,
+		cardKey.ValidityType,
+		cardKey.ExpiresAt,
+		cardKey.IsActive,
+		cardKey.CreatedByID,
+		cardKey.CreatedAt,
+	).Scan(&cardKey.ID)
+}
+
+// FindAll 获取所有卡密
+func (r *CardKeyRepository) FindAll() ([]*models.CardKey, error) {
+	rows, err := r.db.Query(`
+		SELECT id, key, max_uses, used_count, validity_type, expires_at, is_active, created_by_id, created_at
+		FROM card_keys ORDER BY created_at DESC
+	`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var cardKeys []*models.CardKey
+	for rows.Next() {
+		ck := &models.CardKey{}
+		if err := rows.Scan(
+			&ck.ID, &ck.Key, &ck.MaxUses, &ck.UsedCount,
+			&ck.ValidityType, &ck.ExpiresAt, &ck.IsActive,
+			&ck.CreatedByID, &ck.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		cardKeys = append(cardKeys, ck)
+	}
+	return cardKeys, nil
+}
+
+// FindAllPaginated 分页获取卡密
+func (r *CardKeyRepository) FindAllPaginated(page, pageSize int) ([]*models.CardKey, error) {
+	offset := (page - 1) * pageSize
+	rows, err := r.db.Query(`
+		SELECT id, key, max_uses, used_count, validity_type, expires_at, is_active, created_by_id, created_at
+		FROM card_keys ORDER BY created_at DESC
+		LIMIT $1 OFFSET $2
+	`, pageSize, offset)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var cardKeys []*models.CardKey
+	for rows.Next() {
+		ck := &models.CardKey{}
+		if err := rows.Scan(
+			&ck.ID, &ck.Key, &ck.MaxUses, &ck.UsedCount,
+			&ck.ValidityType, &ck.ExpiresAt, &ck.IsActive,
+			&ck.CreatedByID, &ck.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		cardKeys = append(cardKeys, ck)
+	}
+	return cardKeys, nil
+}
+
+// Count 获取卡密总数
+func (r *CardKeyRepository) Count() (int, error) {
+	var count int
+	err := r.db.QueryRow(`SELECT COUNT(*) FROM card_keys`).Scan(&count)
+	return count, err
+}
+
+// Delete 删除单个卡密
+func (r *CardKeyRepository) Delete(id int) error {
+	_, err := r.db.Exec(`DELETE FROM card_keys WHERE id = $1`, id)
+	return err
+}
+
+// BatchDelete 批量删除卡密
+func (r *CardKeyRepository) BatchDelete(ids []int) error {
+	if len(ids) == 0 {
+		return nil
+	}
+	// 构建 IN 子句
+	query := `DELETE FROM card_keys WHERE id = ANY($1)`
+	_, err := r.db.Exec(query, pq.Array(ids))
+	return err
+}
+
+// ToggleActive 切换卡密激活状态
+func (r *CardKeyRepository) ToggleActive(id int, isActive bool) error {
+	_, err := r.db.Exec(`UPDATE card_keys SET is_active = $1 WHERE id = $2`, isActive, id)
+	return err
+}