refactor(tests): Update all test files to use TestServerSetup pattern

cmd/server/tests/goroutine_leak_test.go

@@ -18,8 +18,7 @@ func TestGoroutineCleanup(t *testing.T) {
 	t.Logf("Initial goroutine count: %d", initialGoroutines)
 
 	// Start server
-	ts, _, _ := setupTestServer(t)
-	defer ts.Close()
+	setup := setupTestServer(t)
 
 	// Wait for startup
 	time.Sleep(200 * time.Millisecond)