feat: 初始化 ChatGPT Team 管理后端项目

- 添加用户认证模块 (JWT + 密码管理)
- 添加 ChatGPT 账户管理功能
- 添加卡密管理功能 (创建、批量生成、查询)
- 添加邀请功能
- 配置数据库迁移和路由系统

internal/models/system_setting.go

@@ -0,0 +1,42 @@
+package models
+
+import (
+	"database/sql"
+)
+
+// ValueType 配置值类型枚举
+type ValueType string
+
+const (
+	ValueTypeString ValueType = "string"
+	ValueTypeInt    ValueType = "int"
+	ValueTypeFloat  ValueType = "float"
+	ValueTypeBool   ValueType = "bool"
+	ValueTypeJSON   ValueType = "json"
+)
+
+// SystemSetting 系统配置表
+type SystemSetting struct {
+	ID          int            `json:"id"`
+	Key         string         `json:"key"`
+	Value       string         `json:"value"`
+	ValueType   ValueType      `json:"value_type"`
+	Description sql.NullString `json:"description"`
+	UpdatedAt   sql.NullTime   `json:"updated_at"`
+}
+
+// TableName 返回表名
+func (SystemSetting) TableName() string {
+	return "system_settings"
+}
+
+// 默认配置键名常量
+const (
+	SettingTurnstileEnabled       = "turnstile_enabled"
+	SettingTurnstileSiteKey       = "turnstile_site_key"
+	SettingTurnstileSecretKey     = "turnstile_secret_key"
+	SettingTokenCheckInterval     = "token_check_interval"
+	SettingTokenFailureThreshold  = "token_failure_threshold"
+	SettingInvitationValidityDays = "invitation_validity_days"
+	SettingSiteTitle              = "site_title"
+)