fix: standardize trip name display with arrow separators app-wide

- Add `displayName` computed property to Trip model that always
  generates city list with " → " separator for consistent display
- Replace all `trip.name` usages with `trip.displayName` in UI files
- Update SuggestedTripsGenerator to use " → " separator
- Update PDFGenerator to use displayName for PDF titles

This ensures all trip names display consistently regardless of when
the trip was created or how the name was originally stored.

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

SportsTime/Features/Home/Views/Variants/LuxuryEditorial/HomeContent_LuxuryEditorial.swift

@@ -227,7 +227,7 @@ struct HomeContent_LuxuryEditorial: View {
             }
 
             // Title
-            Text(trip.name)
+            Text(trip.displayName)
                 .font(.system(size: 18, weight: .regular, design: .serif))
                 .foregroundStyle(textPrimary)
                 .lineLimit(2)
@@ -293,7 +293,7 @@ struct HomeContent_LuxuryEditorial: View {
                                 .frame(width: 20)
 
                             VStack(alignment: .leading, spacing: 4) {
-                                Text(trip.name)
+                                Text(trip.displayName)
                                     .font(.system(size: 16, weight: .regular, design: .serif))
                                     .foregroundStyle(textPrimary)