fix: change token model_limits column from varchar(1024) to text

Fixes #3033 — users with many model limits hit PostgreSQL's varchar
length constraint. The text type is supported across all three
databases (SQLite, MySQL, PostgreSQL) with no length restriction.

model/token.go

@@ -23,7 +23,7 @@ type Token struct {
 	RemainQuota        int            `json:"remain_quota" gorm:"default:0"`
 	UnlimitedQuota     bool           `json:"unlimited_quota"`
 	ModelLimitsEnabled bool           `json:"model_limits_enabled"`
-	ModelLimits        string         `json:"model_limits" gorm:"type:varchar(1024);default:''"`
+	ModelLimits        string         `json:"model_limits" gorm:"type:text"`
 	AllowIps           *string        `json:"allow_ips" gorm:"default:''"`
 	UsedQuota          int            `json:"used_quota" gorm:"default:0"` // used quota
 	Group              string         `json:"group" gorm:"default:''"`