Fix multi-day all-day events to display across all days they span

All-day events spanning multiple days were only showing on their start date.
For example, a "Vacation (Dec 20-25)" event would only appear on Dec 20th.

Root cause: Logic only checked events stored in each day's HashMap entry,
missing events that span into other days.

Solution:
- Modified all-day event collection to search all events across all days
- Added event_spans_date() helper function to check if event spans given date
- Properly handles iCalendar dtend convention (day after event ends)
- Added deduplication to prevent duplicate events from multiple day buckets
- Removed unused day_events variable

Result: Multi-day all-day events now correctly appear on every day they span,
while single-day events continue to work as before.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/src/components/week_view.rs

@@ -316,10 +316,19 @@ pub fn week_view(props: &WeekViewProps) -> Html {
                     week_days.iter().map(|date| {
                         let is_today = *date == props.today;
                         let weekday_name = get_weekday_name(date.weekday());
-                        let day_events = props.events.get(date).cloned().unwrap_or_default();
                         
-                        // Filter for all-day events only
-                        let all_day_events: Vec<_> = day_events.iter().filter(|event| event.all_day).collect();
+                        // Collect all-day events that span this date (from any day in the week)
+                        let mut all_day_events: Vec<&VEvent> = Vec::new();
+                        for events_list in props.events.values() {
+                            for event in events_list {
+                                if event.all_day && event_spans_date(event, *date) {
+                                    all_day_events.push(event);
+                                }
+                            }
+                        }
+                        // Remove duplicates (same event might appear in multiple day buckets)
+                        all_day_events.sort_by_key(|e| &e.uid);
+                        all_day_events.dedup_by_key(|e| &e.uid);
 
                         html! {
                             <div class={classes!("week-day-header", if is_today { Some("today") } else { None })}>
@@ -1308,3 +1317,19 @@ fn calculate_event_layout(events: &[VEvent], date: NaiveDate, time_increment: u3
     
     event_columns
 }
+
+// Check if an all-day event spans the given date
+fn event_spans_date(event: &VEvent, date: NaiveDate) -> bool {
+    let start_date = event.dtstart.with_timezone(&Local).date_naive();
+    let end_date = if let Some(dtend) = event.dtend {
+        // For all-day events, dtend is often set to the day after the last day
+        // So we need to subtract a day to get the actual last day of the event
+        dtend.with_timezone(&Local).date_naive() - chrono::Duration::days(1)
+    } else {
+        // Single day event
+        start_date
+    };
+    
+    // Check if the given date falls within the event's date range
+    date >= start_date && date <= end_date
+}