Add supplements, kettlebell, calendar, push notifications, and PWA support

- Supplement tracking: CRUD endpoints, /today, /logs, Supplements page
- Kettlebell workouts: session tracking, analytics endpoint, ActiveSession page
- Calendar module: events CRUD, calendar components
- Push notifications: VAPID keys, PushSubscription model, APScheduler reminders,
  service worker with push/notificationclick handlers, Profile notifications UI
- PWA: vite-plugin-pwa, manifest, icons, service worker generation
- Frontend: TypeScript types, API modules, ConfirmModal, toast notifications
- Auth fixes: password hashing, nutrition endpoint auth
- CLAUDE.md: project documentation and development guide

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

backend/app/scheduler.py

@@ -0,0 +1,47 @@
+from datetime import datetime, timezone
+
+import pytz
+from apscheduler.schedulers.background import BackgroundScheduler
+from apscheduler.triggers.cron import CronTrigger
+from sqlmodel import Session, select
+
+from app.db import engine
+from app.models.push_subscription import PushSubscription
+
+scheduler = BackgroundScheduler(timezone="UTC")
+
+
+def send_supplement_reminders() -> None:
+    from app.api.v1.endpoints.push import send_push
+
+    now_utc = datetime.now(timezone.utc)
+    with Session(engine) as session:
+        subs = session.exec(
+            select(PushSubscription).where(PushSubscription.is_active == True)  # noqa: E712
+        ).all()
+        due = []
+        for sub in subs:
+            try:
+                tz = pytz.timezone(sub.timezone)
+                local_now = now_utc.astimezone(tz)
+                if local_now.hour == sub.reminder_hour and local_now.minute == sub.reminder_minute:
+                    due.append(sub)
+            except Exception:
+                pass
+        if due:
+            send_push(due, title="Supplement Reminder", body="Time to log your supplements for today!", session=session)
+            session.commit()
+
+
+def start_scheduler() -> None:
+    scheduler.add_job(
+        send_supplement_reminders,
+        CronTrigger(minute="*"),
+        id="supplement_reminders",
+        replace_existing=True,
+    )
+    scheduler.start()
+
+
+def stop_scheduler() -> None:
+    scheduler.shutdown(wait=False)