fix(auth): change InternalAuthFilter to use @Singleton and add HTTP tests for secret validation

modules/security/src/main/scala/de/nowchess/security/InternalAuthFilter.scala

@@ -1,6 +1,6 @@
 package de.nowchess.security
 
-import jakarta.enterprise.context.ApplicationScoped
+import jakarta.inject.Singleton
 import jakarta.ws.rs.container.{ContainerRequestContext, ContainerRequestFilter}
 import jakarta.ws.rs.core.Response
 import jakarta.ws.rs.ext.Provider
@@ -9,7 +9,7 @@ import scala.compiletime.uninitialized
 
 @Provider
 @InternalOnly
-@ApplicationScoped
+@Singleton
 class InternalAuthFilter extends ContainerRequestFilter:
 
   @ConfigProperty(name = "nowchess.internal.secret", defaultValue = "")