Fix event width bug: timed events showing half-width when all-day events exist

Timed events were incorrectly displaying at half-width when all-day events
existed on the same day, even though all-day events display separately at
the top of the calendar and don't visually overlap with timed events.

Root cause: The overlap calculation logic was including all-day events when
determining width splits for timed events.

Solution:
- Modified calculate_event_layout() to exclude all-day events from filtering
- Updated events_overlap() to return false if either event is all-day
- All-day events now don't participate in timed event width calculations

Result: Timed events display at full width unless they actually overlap
with other timed events, while all-day events continue to display correctly
in their separate section.

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

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

frontend/src/components/week_view.rs

@@ -1193,6 +1193,11 @@ fn calculate_event_position(event: &VEvent, date: NaiveDate, time_increment: u32
 
 // Check if two events overlap in time
 fn events_overlap(event1: &VEvent, event2: &VEvent) -> bool {
+    // All-day events don't overlap with timed events for width calculation purposes
+    if event1.all_day || event2.all_day {
+        return false;
+    }
+    
     let start1 = event1.dtstart.with_timezone(&Local).naive_local();
     let end1 = if let Some(end) = event1.dtend {
         end.with_timezone(&Local).naive_local()
@@ -1214,10 +1219,15 @@ fn events_overlap(event1: &VEvent, event2: &VEvent) -> bool {
 // Calculate layout columns for overlapping events
 fn calculate_event_layout(events: &[VEvent], date: NaiveDate, time_increment: u32) -> Vec<(usize, usize)> {
     
-    // Filter and sort events that should appear on this date
+    // Filter and sort events that should appear on this date (excluding all-day events)
     let mut day_events: Vec<_> = events.iter()
         .enumerate()
         .filter_map(|(idx, event)| {
+            // Skip all-day events as they don't participate in timed event overlap calculations
+            if event.all_day {
+                return None;
+            }
+            
             let (_, _, _) = calculate_event_position(event, date, time_increment);
             let local_start = event.dtstart.with_timezone(&Local);
             let event_date = local_start.date_naive();