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/Flighty/HomeContent_Flighty.swift

@@ -221,7 +221,7 @@ struct HomeContent_Flighty: View {
             }
 
             VStack(alignment: .leading, spacing: 8) {
-                Text(trip.name)
+                Text(trip.displayName)
                     .font(.system(size: 16, weight: .semibold))
                     .foregroundStyle(textPrimary)
                     .lineLimit(1)
@@ -310,7 +310,7 @@ struct HomeContent_Flighty: View {
             }
 
             VStack(alignment: .leading, spacing: 3) {
-                Text(trip.name)
+                Text(trip.displayName)
                     .font(.system(size: 15, weight: .medium))
                     .foregroundStyle(textPrimary)
                     .lineLimit(1)