fix(itinerary): improve drag-drop reordering with stable anchors and visual feedback

- Add visual drop target indicator showing where items will land
- Use stable travel anchor IDs (city names) instead of UUIDs that regenerate
- Fix findDayForTravelSegment to look forward to arrival day, not backward
- Add moveItemToBeginning() for inserting at position 0 when dropping on sections
- Sort custom items by sortOrder in all filters
- Sync shifted items to CloudKit after reorder
- Add opaque backgrounds to CustomItemRow and TravelSection to hide timeline

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

SportsTime/Features/Trip/Views/CustomItemRow.swift

@@ -43,8 +43,17 @@ struct CustomItemRow: View {
             }
             .padding(.horizontal, Theme.Spacing.md)
             .padding(.vertical, Theme.Spacing.sm)
-            .background(Theme.warmOrange.opacity(0.08))
-            .cornerRadius(8)
+            .background {
+                // Opaque base + semi-transparent accent
+                RoundedRectangle(cornerRadius: 8)
+                    .fill(Theme.cardBackground(colorScheme))
+                RoundedRectangle(cornerRadius: 8)
+                    .fill(Theme.warmOrange.opacity(0.1))
+            }
+            .overlay {
+                RoundedRectangle(cornerRadius: 8)
+                    .strokeBorder(Theme.warmOrange.opacity(0.3), lineWidth: 1)
+            }
         }
         .buttonStyle(.plain)
         .contextMenu {