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/ArtDeco/HomeContent_ArtDeco.swift

@@ -347,7 +347,7 @@ struct HomeContent_ArtDeco: View {
             }
 
             VStack(alignment: .leading, spacing: 6) {
-                Text(trip.name.uppercased())
+                Text(trip.displayName.uppercased())
                     .font(.system(size: 14, weight: .bold))
                     .tracking(1)
                     .foregroundStyle(textPrimary)
@@ -430,7 +430,7 @@ struct HomeContent_ArtDeco: View {
                             decoDiamond
                                 .foregroundStyle(decoTeal)
 
-                            Text(trip.name)
+                            Text(trip.displayName)
                                 .font(.system(size: 14, weight: .medium))
                                 .foregroundStyle(textPrimary)