Remove Socket.IO dependencies and Socket infrastructure

- Remove socket.io-client npm package
- Remove Socket.IO from gulpfile.js
- Remove API_PUBLIC_WS_URL config variable from all environments
- Remove Socket CSP directives (cdn.socket.io, wss:// URLs)
- Remove unused data-host attribute from job template
- Update test_headers.py to remove Socket.IO assertions
- Update deployment configs (manifest.yml, deploy-config/*.yml, .github/workflows/*.yml)

app/templates/views/jobs/job.html

@@ -15,7 +15,7 @@
     {% if not job.finished_processing %}
       <p class="max-width-full">Status updates automatically while processing. Refresh the page if needed.</p>
     {% endif %}
-    <div data-job-id="{{ job.id }}" data-job-finished="{{ 'true' if job.finished_processing else 'false' }}" data-host="{{ api_public_url }}">
+    <div data-job-id="{{ job.id }}" data-job-finished="{{ 'true' if job.finished_processing else 'false'}}">
       <div class='tabs ajax-block-container' data-key="counts">
         {{ pill(counts, status, {'smaller': True}) }}
       </div>