feat(sub): auto-detect subscription format by User-Agent (Updated) (#5826)

* feat(settings): add subscription format controls

* feat(sub): auto-detect subscription formats

* fix(xray): validate balancer regexes before save

* Revert "fix(xray): validate balancer regexes before save"

This reverts commit 8a208ce71b.

* doc(endpoints): align indent spaces

* doc(settings): improve error message formatting in validateSubUserAgentRegex

- Use NewErrorf with proper formatting instead of NewError with string concatenation
- Add comment explaining the rationale for returning original pattern value
- This preserves the intentional design where empty input is stored as empty
  in the DB and inherited as the runtime default at read time

---------

Co-authored-by: Tomilla <5007859+Tomilla@users.noreply.github.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

internal/sub/json_service.go

@@ -58,7 +58,7 @@ func NewSubJsonService(mux string, rules string, finalMask string, subService *S
 }
 
 // GetJson generates a JSON subscription configuration for the given subscription ID and host.
-func (s *SubJsonService) GetJson(subId string, host string) (string, string, error) {
+func (s *SubJsonService) GetJson(subId string, host string, alwaysReturnArray bool) (string, string, error) {
 	subReq := s.SubService.ForRequest(host)
 	subReq.subscriptionBody = true
 	inbounds, err := subReq.getInboundsBySubId(subId)
@@ -125,9 +125,8 @@ func (s *SubJsonService) GetJson(subId string, host string) (string, string, err
 	}
 	traffic, _ := subReq.AggregateTrafficByEmails(emails)
 
-	// Combile outbounds
 	var finalJson []byte
-	if len(configArray) == 1 {
+	if len(configArray) == 1 && !alwaysReturnArray {
 		finalJson, _ = json.MarshalIndent(configArray[0], "", "  ")
 	} else {
 		finalJson, _ = json.MarshalIndent(configArray, "", "  ")