Reduce Garmin sync frequency to 3 times daily

Sync at 08:00, 14:00, and 22:00 UTC instead of every hour.
Garmin data updates once daily so hourly was excessive.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/instrumentation.ts

@@ -49,14 +49,14 @@ export async function register() {
       triggerCronEndpoint("notifications", "Notifications");
     });
 
-    // Schedule Garmin sync at 30 minutes past every hour
-    cron.default.schedule("30 * * * *", () => {
+    // Schedule Garmin sync 3 times daily (8 AM, 2 PM, 10 PM UTC)
+    cron.default.schedule("0 8,14,22 * * *", () => {
       console.log("[cron] Triggering Garmin sync...");
       triggerCronEndpoint("garmin-sync", "Garmin sync");
     });
 
     console.log(
-      "[cron] Scheduler started - notifications at :00, Garmin sync at :30",
+      "[cron] Scheduler started - notifications hourly, Garmin sync at 08:00/14:00/22:00 UTC",
     );
   }
 }