Add Live Queue slide to kiosk rotation

- Added a third kiosk slide showing the active customer queue.
- Customer names are derived from the local-part of their email address.
- Statuses are mapped to friendly labels:
    pending -> Received
    prompt_ready / songs_uploaded -> Trollgorithm Recording in Studio
    revisions_requested -> Waiting for Customer Response
    awaiting_payment -> Payment Due
- Completed/delivered statuses are not shown.
- If the queue overflows, a note points customers to the status page.
- Added queue-only mode (kiosk_cycle_seconds = 1) and updated the
  cycle logic to rotate QR -> pricing -> queue.
- Updated /admin/settings help text for the new mode.

Bumps version to 0.5.3.

templates/admin/settings.html

@@ -272,12 +272,12 @@
       <!-- Kiosk cycle -->
       <div class="section">
         <h2>Kiosk Display Mode</h2>
-        <p class="copy-hint">Set how the public <a href="{{ url_for('kiosk') }}" target="_blank" rel="noopener noreferrer">/kiosk</a> page cycles. Use -1 for QR only, 0 for pricing only, or 5+ seconds to cycle between them.</p>
+        <p class="copy-hint">Set how the public <a href="{{ url_for('kiosk') }}" target="_blank" rel="noopener noreferrer">/kiosk</a> page cycles. Use -1 for QR only, 0 for pricing only, 1 for queue only, or 5+ seconds to cycle between QR, pricing, and queue.</p>
         <form method="POST">
           <input type="hidden" name="action" value="save_kiosk_cycle">
           <label for="kiosk_cycle_seconds">Kiosk cycle seconds</label>
           <input type="number" id="kiosk_cycle_seconds" name="kiosk_cycle_seconds" value="{{ current_kiosk_cycle_seconds }}" min="-1">
-          <p class="copy-hint">Examples: -1 = QR only, 0 = pricing only, 10 = swap every 10 seconds.</p>
+          <p class="copy-hint">Examples: -1 = QR only, 0 = pricing only, 1 = queue only, 10 = rotate QR → pricing → queue every 10 seconds.</p>
           <button type="submit">Save Kiosk Mode</button>
         </form>
       </div>