feat(sub): per-inbound sort order for subscription links

Add a subSortIndex field to inbounds that controls the order of links
in subscription output only: the raw sub body, the HTML sub page, and
the JSON/Clash formats (all served from the same query). Lower values
come first; ties keep id order. The panel inbound list is unaffected.

The value is editable in the inbound form next to the share-address
fields, propagates to nodes via wireInbound, and follows the usual
node-sync rules (copied on import, mirrored while not dirty, never a
structural change).

Rescoped from #5214 by @Ponywka.

internal/database/db.go

@@ -91,6 +91,9 @@ func initModels() error {
 	if err := pruneOrphanedClientInbounds(); err != nil {
 		return err
 	}
+	if err := normalizeInboundSubSortIndex(); err != nil {
+		return err
+	}
 	if IsPostgres() {
 		if err := resyncPostgresSequences(db, models); err != nil {
 			log.Printf("Error resyncing postgres sequences: %v", err)
@@ -123,6 +126,21 @@ func pruneOrphanedClientInbounds() error {
 	return nil
 }
 
+// normalizeInboundSubSortIndex lifts sub_sort_index values below the 1-based
+// minimum (rows written by builds that defaulted the column to 0, or by nodes
+// predating the field) so they cannot sort ahead of explicitly ranked inbounds.
+func normalizeInboundSubSortIndex() error {
+	res := db.Exec("UPDATE inbounds SET sub_sort_index = 1 WHERE sub_sort_index < 1")
+	if res.Error != nil {
+		log.Printf("Error normalizing inbound sub_sort_index: %v", res.Error)
+		return res.Error
+	}
+	if res.RowsAffected > 0 {
+		log.Printf("Normalized sub_sort_index on %d inbound(s)", res.RowsAffected)
+	}
+	return nil
+}
+
 func isIgnorableDuplicateColumnErr(err error, mdl any) bool {
 	if err == nil {
 		return false

internal/database/model/model.go

@@ -50,6 +50,7 @@ type Inbound struct {
 	Down                 int64                `json:"down" form:"down"`                                                                                                                                             // Download traffic in bytes
 	Total                int64                `json:"total" form:"total"`                                                                                                                                           // Total traffic limit in bytes
 	Remark               string               `json:"remark" form:"remark" example:"VLESS-443"`                                                                                                                     // Human-readable remark
+	SubSortIndex         int                  `json:"subSortIndex" form:"subSortIndex" gorm:"default:1" validate:"omitempty,gte=1" example:"1"`                                                                     // 1-based sort order of this inbound's links in subscription output only (lower first; ties by id)
 	Enable               bool                 `json:"enable" form:"enable" gorm:"index:idx_enable_traffic_reset,priority:1" example:"true"`                                                                         // Whether the inbound is enabled
 	ExpiryTime           int64                `json:"expiryTime" form:"expiryTime"`                                                                                                                                 // Expiration timestamp
 	TrafficReset         string               `json:"trafficReset" form:"trafficReset" gorm:"default:never;index:idx_enable_traffic_reset,priority:2" validate:"omitempty,oneof=never hourly daily weekly monthly"` // Traffic reset schedule