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/sub/service.go

@@ -284,7 +284,7 @@ func (s *SubService) getInboundsBySubId(subId string) ([]*model.Inbound, error)
 		WHERE
 			inbounds.protocol in ('vmess','vless','trojan','shadowsocks','hysteria')
 			AND clients.sub_id = ? AND inbounds.enable = ?
-	)`, subId, true).Find(&inbounds).Error
+	)`, subId, true).Order("sub_sort_index ASC").Order("id ASC").Find(&inbounds).Error
 	if err != nil {
 		return nil, err
 	}