Add program reminders and category filtering to the guide UI

Enhance health diagnostics with EPG quality and source metrics

src/js/config.js

@@ -11,6 +11,8 @@ const DEFAULT_M3U_URL = EPG_SOURCES[0]?.m3u_url ?? '';
 const PX_PER_MIN = 5;
 const GRID_HOURS = 72;
 const CORS_PROXY = '/proxy.php?url=';
+const REMINDER_STORAGE_KEY = 'gridtv-reminders';
+const REMINDER_OFFSET_MS = 15 * 60 * 1000;
 
 // Anchor the grid 2 hours before "now", rounded down to the previous quarter-hour.
 const _d = new Date();