feat(trip): redesign add custom item UI with polished visuals

Replace confusing dual-mode AddItemSheet with streamlined QuickAddItemSheet:
- Single flow with optional location (vs Search/Custom toggle)
- Card-based layout with shadows, borders, and theme colors
- Enhanced CategoryPicker with emoji circles and press animations
- Separate PlaceSearchSheet for focused location search
- Improved header button with capsule style and accessibility labels

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

SportsTime/Features/Trip/Views/AddItemSheet.swift

@@ -37,6 +37,9 @@ enum ItemCategory: String, CaseIterable {
     }
 }
 
+/// Legacy sheet for adding/editing custom itinerary items.
+/// - Note: Use `QuickAddItemSheet` instead for new code.
+@available(*, deprecated, message: "Use QuickAddItemSheet instead")
 struct AddItemSheet: View {
     @Environment(\.dismiss) private var dismiss
     @Environment(\.colorScheme) private var colorScheme