fix(panel): streamline system settings and server creation

Use shared action buttons and default to the login space. Allow staff to save startup-only experience settings while running and request a durable restart through the existing operator flow.

Grant the API PVC list permission needed to detect retained worlds before server creation, and show internal failures with a request ID. Cover permission, maintenance, restart and UI behavior with regression checks.

internal/naming/naming.go

@@ -46,6 +46,8 @@ const (
 	// reachable only after the login gate passes a player through, so it must
 	// never be used as a fallback target (that would bypass the gate).
 	SystemLobbyServer = "lobby"
+	// ExperienceConfigFile is read by the system plugins only at startup.
+	ExperienceConfigFile = "felis-experience.json"
 )
 
 // IsSystemServer identifies platform services whose reserved names may be managed