De-hardcode ticket URL and cluster name; improve diagnostic polling UX

app.py:
- Context processor injects config.ticket_api.web_url into all templates
  (falls back to 'http://t.lotusguild.org/ticket/' if not set in config)

templates/base.html:
- Inject GANDALF_CONFIG JS global with ticket_web_url before app.js loads

static/app.js:
- Use GANDALF_CONFIG.ticket_web_url instead of hardcoded domain

templates/index.html:
- Use {{ config.ticket_api.web_url }} Jinja var instead of hardcoded domain

monitor.py:
- CLUSTER_NAME constant kept as default; NetworkMonitor now reads cluster_name
  from config monitor.cluster_name, falling back to the constant
- All CLUSTER_NAME references inside class methods replaced with self.cluster_name

templates/inspector.html:
- pollDiagnostic() .catch() now clears interval and shows error message instead
  of silently ignoring network failures during active polling

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/base.html

@@ -41,6 +41,11 @@
     {% block content %}{% endblock %}
   </main>
 
+  <script>
+    const GANDALF_CONFIG = {
+      ticket_web_url: "{{ config.get('ticket_api', {}).get('web_url', 'http://t.lotusguild.org/ticket/') }}"
+    };
+  </script>
   <script src="{{ url_for('static', filename='app.js') }}"></script>
   {% block scripts %}{% endblock %}
 </body>