fix: tag flaky GitHub API test as :integration

The test makes a real HTTP call to GitHub which can fail or return
different responses depending on network conditions, rate limits, etc.

Tagged as :integration to exclude from normal test runs, consistent
with other GitHub API tests in ReleaseCheckerTest.

test/towerops_web/controllers/api/v1/agent_release_webhook_controller_test.exs

@@ -32,6 +32,7 @@ defmodule ToweropsWeb.Api.V1.AgentReleaseWebhookControllerTest do
   end
 
   describe "create/2 response" do
+    @tag :integration
     test "returns 502 when GitHub API is unavailable", %{conn: conn} do
       # In test environment, GitHub API returns 404 (private repo, no auth token).
       # The controller should surface this as a 502.