fix: cache_ttl config validation; ticket_web_url via tojson in base.html

- app.py: wrap int(cache_ttl) in try/except so a misconfigured non-integer value falls back to 3600 instead of raising ValueError
- base.html: use Jinja2 tojson filter for ticket_web_url to ensure proper JS string escaping regardless of URL contents

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

templates/base.html

@@ -313,7 +313,7 @@
 
   <script>
     const GANDALF_CONFIG = {
-      ticket_web_url: "{{ config.get('ticket_api', {}).get('web_url', 'http://t.lotusguild.org/ticket/') }}"
+      ticket_web_url: {{ config.get('ticket_api', {}).get('web_url', 'http://t.lotusguild.org/ticket/') | tojson }}
     };
   </script>
   <script src="{{ url_for('static', filename='app.js') }}"></script>