Refactor Steam login initialization to remove unnecessary response and add nonce handling

api/Authenticator.api

@@ -17,9 +17,7 @@ type (
 
 type (
 	SteamLoginInitReq  {}
-	SteamLoginInitResp {
-		RedirectUrl string `json:"redirectUrl"`
-	}
+// No response needed - endpoint will redirect directly
 )
 
 type (
@@ -55,10 +53,10 @@ service Authenticator {
 
 	@doc (
 		summary:     "Initiate Steam login"
-		description: "Redirects user to Steam OpenID login page"
+		description: "Redirects user to Steam OpenID login page with nonce for security"
 	)
 	@handler steamLoginInitHandler
-	get /steam/login (SteamLoginInitReq) returns (SteamLoginInitResp)
+	get /steam/login (SteamLoginInitReq)
 
 	@doc (
 		summary:     "Steam login callback"