small fix: log

Author: phanthaiduong22

app/backend/Program.cs

@@ -24,9 +24,9 @@
     static string? GetEnvVar(string key) => Environment.GetEnvironmentVariable(key);
 
     var endpoint = GetEnvVar("AZURE_SIGNALR_ENDPOINT")
-        ?? throw new InvalidOperationException("Azure:SignalR:Endpoint is not configured");
+        ?? throw new InvalidOperationException("AZURE_SIGNALR_ENDPOINT is not configured");
     var clientId = GetEnvVar("AZURE_CLIENT_ID")
-        ?? throw new InvalidOperationException("Azure:SignalR:IdentityClientId is not configured");
+        ?? throw new InvalidOperationException("AZURE_CLIENT_ID is not configured");
 
     options.Endpoints = new[] 
     {