feat(simnet): add SimNet protocol end-to-end support

- model: SimNet protocol fields + NormalizeSimnet; type+port protocol uniqueness
- server config: OmnXT runtime config delivery via compatible() simnet case
- credentials: derive per-user psk/key_id from subscription (pkg/simnet), no new table
- subscription: adapter buildOmnxtSimnetConfigs + base64 buildOmnxtProtocolLinks + OmnXT SimNet application (migration 02161)
- UA gating: hide experimental protocols from non first-party clients (download + JSON node-list)
- admin: normalize simnet on create/update and on GET responses
- tests: 21 simnet unit tests; full suite green

internal/handler/public/subscribe/queryUserSubscribeNodeListHandler.go

@@ -11,7 +11,7 @@ import (
 func QueryUserSubscribeNodeListHandler(svcCtx *svc.ServiceContext) func(c *gin.Context) {
 	return func(c *gin.Context) {
 
-		l := subscribe.NewQueryUserSubscribeNodeListLogic(c.Request.Context(), svcCtx)
+		l := subscribe.NewQueryUserSubscribeNodeListLogic(c.Request.Context(), svcCtx, c.GetHeader("User-Agent"))
 		resp, err := l.QueryUserSubscribeNodeList()
 		result.HttpResult(c, resp, err)
 	}