feat(web): show multi-day calendar events on every day they span

TimelineItemView wraps a TimelineItem with a per-render-day
MultiDayVariant (starts/ends/spans/none). HandleTimeline's bucketing now
places a multi-day event into both TodayItems and TomorrowItems when it
touches both, instead of only the list matching its start day.

1 files changed, 75 insertions, 9 deletions

diff --git a/internal/handlers/timeline.go b/internal/handlers/timeline.go
index 2c3c6b6..e8eadde 100644
--- a/internal/handlers/timeline.go
+++ b/internal/handlers/timeline.go
@@ -10,11 +10,60 @@ import (
 	"task-dashboard/internal/models"
 )
 
+// TimelineItemView wraps a TimelineItem with how it should render for one
+// specific day (Today or Tomorrow). MultiDayVariant is "" for a normal
+// single-day item; "starts"/"ends"/"spans" for a calendar event whose
+// Start and End fall on different calendar days -- see isMultiDayEvent.
+type TimelineItemView struct {
+	models.TimelineItem
+	MultiDayVariant string
+}
+
+// dateOnly strips the time-of-day, keeping the calendar day in t's own location.
+func dateOnly(t time.Time) time.Time {
+	return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
+}
+
+// isMultiDayEvent reports whether item is a calendar event whose Start and
+// End fall on different calendar days (in the display timezone). Only
+// events are ever considered multi-day -- tasks, cards, meals, and Google
+// Tasks keep their existing single-day rendering unconditionally.
+func isMultiDayEvent(item models.TimelineItem) bool {
+	if item.Type != models.TimelineItemTypeEvent || item.EndTime == nil {
+		return false
+	}
+	tz := config.GetDisplayTimezone()
+	return !dateOnly(item.EndTime.In(tz)).Equal(dateOnly(item.Time.In(tz)))
+}
+
+// multiDayVariant returns how a multi-day item should render on renderDay:
+// "starts" if renderDay is the item's start day, "ends" if renderDay is its
+// end day, "spans" if renderDay falls strictly between them, or "" if
+// renderDay doesn't fall within the item's span at all. Caller must have
+// already confirmed isMultiDayEvent(item) so item.EndTime is non-nil.
+func multiDayVariant(item models.TimelineItem, renderDay time.Time) string {
+	tz := config.GetDisplayTimezone()
+	startDay := dateOnly(item.Time.In(tz))
+	endDay := dateOnly(item.EndTime.In(tz))
+	day := dateOnly(renderDay.In(tz))
+
+	switch {
+	case day.Equal(startDay):
+		return "starts"
+	case day.Equal(endDay):
+		return "ends"
+	case day.After(startDay) && day.Before(endDay):
+		return "spans"
+	default:
+		return ""
+	}
+}
+
 // TimelineData holds grouped timeline items for the template
 type TimelineData struct {
-	TodayItems    []models.TimelineItem
-	TomorrowItems []models.TimelineItem
-	LaterItems    []models.TimelineItem
+	TodayItems    []TimelineItemView
+	TomorrowItems []TimelineItemView
+	LaterItems    []TimelineItemView
 	Start         time.Time
 	Days          int
 
@@ -100,13 +149,29 @@ func (h *Handler) HandleTimeline(w http.ResponseWriter, r *http.Request) {
 		NowMinute:     now.Minute(),
 	}
 	for _, item := range items {
+		if isMultiDayEvent(item) {
+			addedToday := false
+			addedTomorrow := false
+			if v := multiDayVariant(item, today); v != "" {
+				data.TodayItems = append(data.TodayItems, TimelineItemView{item, v})
+				addedToday = true
+			}
+			if v := multiDayVariant(item, tomorrow); v != "" {
+				data.TomorrowItems = append(data.TomorrowItems, TimelineItemView{item, v})
+				addedTomorrow = true
+			}
+			if !addedToday && !addedTomorrow {
+				data.LaterItems = append(data.LaterItems, TimelineItemView{item, ""})
+			}
+			continue
+		}
 		switch item.DaySection {
 		case models.DaySectionToday:
-			data.TodayItems = append(data.TodayItems, item)
+			data.TodayItems = append(data.TodayItems, TimelineItemView{item, ""})
 		case models.DaySectionTomorrow:
-			data.TomorrowItems = append(data.TomorrowItems, item)
+			data.TomorrowItems = append(data.TomorrowItems, TimelineItemView{item, ""})
 		case models.DaySectionLater:
-			data.LaterItems = append(data.LaterItems, item)
+			data.LaterItems = append(data.LaterItems, TimelineItemView{item, ""})
 		}
 	}
 
@@ -128,14 +193,15 @@ func (h *Handler) HandleTimeline(w http.ResponseWriter, r *http.Request) {
 // calcCalendarBounds returns start/end hours for calendar view based on timed events.
 // If currentHour >= 0, it's included in the range (for "now" line visibility).
 // Returns hours clamped to 0-23 with 1-hour buffer before/after events.
-func calcCalendarBounds(items []models.TimelineItem, currentHour int) (startHour, endHour int) {
+func calcCalendarBounds(items []TimelineItemView, currentHour int) (startHour, endHour int) {
 	minHour := 23
 	maxHour := 0
 	hasTimedEvents := false
 
 	for _, item := range items {
-		// Skip all-day/overdue items (midnight with no real time)
-		if item.IsAllDay || item.IsOverdue {
+		// Skip all-day/overdue/multi-day items (rendered as all-day-style
+		// rows, not grid slots -- see TimelineItemView.MultiDayVariant)
+		if item.IsAllDay || item.IsOverdue || item.MultiDayVariant != "" {
 			continue
 		}
 		h := item.Time.Hour()