Remove Content-Disposition from iCal feed for Google Calendar compatibility

Google Calendar treats attachment disposition as download instead of
subscription. Remove it so Google properly subscribes to the feed.
Set 1h cache for CDN-friendly serving.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

blueprints/community/calendar/routes.py

@@ -444,8 +444,7 @@ def ical_feed():
             ical_content,
             mimetype='text/calendar; charset=utf-8',
             headers={
-                'Content-Disposition': 'attachment; filename="norda-biznes.ics"',
-                'Cache-Control': 'no-cache, must-revalidate',
+                'Cache-Control': 'public, max-age=3600',
             }
         )
     finally: