ENG-2595 (#3976)

* feat: implement railway secret sync

* fix: railway sync config

* feat: add documentation on railway

* fix: undo mock on-prem change

* lint: fix

* fix: cleanup railway integration

* fix: retry and doc images

* fix: sync fields

* fix: query typo

* Update docs/docs.json

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

backend/src/services/secret-sync/secret-sync-enums.ts

@@ -21,7 +21,8 @@ export enum SecretSync {
   Flyio = "flyio",
   GitLab = "gitlab",
   CloudflarePages = "cloudflare-pages",
-  Zabbix = "zabbix"
+  Zabbix = "zabbix",
+  Railway = "railway"
 }
 
 export enum SecretSyncInitialSyncBehavior {