feat: 支持用户专属分组倍率配置

backend/internal/service/user.go

@@ -21,6 +21,10 @@ type User struct {
 	CreatedAt     time.Time
 	UpdatedAt     time.Time
 
+	// GroupRates 用户专属分组倍率配置
+	// map[groupID]rateMultiplier
+	GroupRates map[int64]float64
+
 	// TOTP 双因素认证字段
 	TotpSecretEncrypted *string    // AES-256-GCM 加密的 TOTP 密钥
 	TotpEnabled         bool       // 是否启用 TOTP
@@ -40,18 +44,20 @@ func (u *User) IsActive() bool {
 
 // CanBindGroup checks whether a user can bind to a given group.
 // For standard groups:
-// - If AllowedGroups is non-empty, only allow binding to IDs in that list.
-// - If AllowedGroups is empty (nil or length 0), allow binding to any non-exclusive group.
+// - Public groups (non-exclusive): all users can bind
+// - Exclusive groups: only users with the group in AllowedGroups can bind
 func (u *User) CanBindGroup(groupID int64, isExclusive bool) bool {
-	if len(u.AllowedGroups) > 0 {
-		for _, id := range u.AllowedGroups {
-			if id == groupID {
-				return true
-			}
-		}
-		return false
+	// 公开分组（非专属）：所有用户都可以绑定
+	if !isExclusive {
+		return true
 	}
-	return !isExclusive
+	// 专属分组：需要在 AllowedGroups 中
+	for _, id := range u.AllowedGroups {
+		if id == groupID {
+			return true
+		}
+	}
+	return false
 }
 
 func (u *User) SetPassword(password string) error {