fix(itinerary): add empty state and single-line date format to DayHeaderRow

- Add isEmpty parameter to show "No items yet, tap + to add" text
- Change date format to single line: "Day 1 - Friday, January 17"
- Update preview to test both empty and non-empty states

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

SportsTime/Features/Trip/Views/ItineraryRows/DayHeaderRow.swift

@@ -10,6 +10,7 @@ import SwiftUI
 struct DayHeaderRow: View {
     let dayNumber: Int
     let date: Date
+    let isEmpty: Bool
     let onAddTapped: () -> Void
 
     @Environment(\.colorScheme) private var colorScheme
@@ -19,24 +20,26 @@ struct DayHeaderRow: View {
     }
 
     var body: some View {
-        HStack {
-            VStack(alignment: .leading, spacing: 2) {
-                Text("Day \(dayNumber)")
+        VStack(alignment: .leading, spacing: 4) {
+            HStack {
+                Text("Day \(dayNumber) - \(formattedDate)")
                     .font(.title3)
                     .fontWeight(.semibold)
                     .foregroundStyle(Theme.textPrimary(colorScheme))
 
-                Text(formattedDate)
-                    .font(.subheadline)
-                    .foregroundStyle(Theme.textSecondary(colorScheme))
+                Spacer()
+
+                Button(action: onAddTapped) {
+                    Image(systemName: "plus.circle.fill")
+                        .font(.title2)
+                        .foregroundStyle(Theme.warmOrange)
+                }
             }
 
-            Spacer()
-
-            Button(action: onAddTapped) {
-                Image(systemName: "plus.circle.fill")
-                    .font(.title2)
-                    .foregroundStyle(Theme.warmOrange)
+            if isEmpty {
+                Text("No items yet, tap + to add")
+                    .font(.subheadline)
+                    .foregroundStyle(Theme.textSecondary(colorScheme))
             }
         }
         .padding(.vertical, Theme.Spacing.sm)
@@ -45,9 +48,14 @@ struct DayHeaderRow: View {
 }
 
 #Preview {
-    VStack {
-        DayHeaderRow(dayNumber: 1, date: Date(), onAddTapped: {})
-        DayHeaderRow(dayNumber: 2, date: Date().addingTimeInterval(86400), onAddTapped: {})
+    VStack(spacing: 16) {
+        // Day with items (not empty)
+        DayHeaderRow(dayNumber: 1, date: Date(), isEmpty: false, onAddTapped: {})
+
+        Divider()
+
+        // Empty day
+        DayHeaderRow(dayNumber: 2, date: Date().addingTimeInterval(86400), isEmpty: true, onAddTapped: {})
     }
     .padding()
     .background(Color.gray.opacity(0.1))