Fix lock overlay z-index and duplicate recurring event notifications

- Lock overlay: z-50 -> z-[100] so it renders above Sheet/Dialog (both z-50)
- Event notifications: skip recurring parent template rows (recurrence_rule
  set + parent_event_id NULL) which duplicate the child instance rows,
  causing double notifications for recurring events

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

backend/app/jobs/notifications.py

@@ -103,6 +103,12 @@ async def _dispatch_events(db: AsyncSession, settings: Settings, now: datetime)
             and_(
                 CalendarEvent.start_datetime >= now,
                 CalendarEvent.start_datetime <= window_end,
+                # Exclude recurring parent templates — they duplicate the child instance rows.
+                # Parent templates have recurrence_rule set but no parent_event_id.
+                ~and_(
+                    CalendarEvent.recurrence_rule != None,  # noqa: E711
+                    CalendarEvent.parent_event_id == None,  # noqa: E711
+                ),
             )
         ).options(selectinload(CalendarEvent.location))
     )

frontend/src/components/layout/LockOverlay.tsx

@@ -56,7 +56,7 @@ export default function LockOverlay() {
   };
 
   return (
-    <div className="fixed inset-0 z-50 flex flex-col items-center justify-center bg-background animate-fade-in">
+    <div className="fixed inset-0 z-[100] flex flex-col items-center justify-center bg-background animate-fade-in">
       <AmbientBackground />
 
       <div className="relative z-10 flex flex-col items-center gap-6 w-full max-w-sm px-4 animate-slide-up">