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>

static/app.js

@@ -135,8 +135,10 @@ function updateEventsTable(events) {
     const supType = e.event_type === 'unifi_device_offline' ? 'unifi_device'
                   : e.event_type === 'interface_down'       ? 'interface'
                   : 'host';
+    const ticketBase = (typeof GANDALF_CONFIG !== 'undefined' && GANDALF_CONFIG.ticket_web_url)
+      ? GANDALF_CONFIG.ticket_web_url : 'http://t.lotusguild.org/ticket/';
     const ticket = e.ticket_id
-      ? `<a href="http://t.lotusguild.org/ticket/${e.ticket_id}" target="_blank"
+      ? `<a href="${ticketBase}${e.ticket_id}" target="_blank"
             class="ticket-link">#${e.ticket_id}</a>`
       : '–';
     return `