Unify capsule, station label and price rating styling

One adaptive tone palette and one shape rule now drive every capsule on
Stations, Favourites, the detail sheet and the Key.

- CapsuleTone: the light/dark palette pairs in one place, resolved through a
  UIColor dynamic provider so a List row that re-renders without rebuilding
  its body still follows an appearance switch. Every pair clears 4.5:1
  foreground-on-background in both appearances (4.96-6.72:1).
- AdaptiveCapsule: capsule at one drawn line, rounded rect at two or more,
  radius 8 -> 10, measuring content before padding so insets cannot inflate
  the line count.
- Listing verdict capsules move from white-on-muted-solid to the tinted
  palette, so Saves, Break even, Costs and Closest station read the same in
  the rows and in the detail sheet.
- Best Value is purple, not green: green stays reserved for a financial
  saving, which is what the Saves capsule beside it means.
- Price dots standardise to 12pt in the app (widget keeps its own 6pt dot;
  PriceRatingDot now takes a diameter so the difference is deliberate).
- Station labels are sentence case with their recommended symbols (medal, tag,
  location.north.fill, trophy) and StationLabelKind replaces the Key's
  string-literal dispatch, so renaming a label can no longer drop a row.
- Key says "Costs", matching the capsule's own headline (was "Costs more").

FuelBoardWatch Watch App/ContentView.swift

@@ -516,8 +516,10 @@ struct ContentView: View {
                             .fontWeight(favourite.isCheapest ? .semibold : .regular)
                             .lineLimit(1)
                         if favourite.isCheapest {
-                            Text("TOP")
-                                .font(.system(size: 9, weight: .bold))
+                            // Sentence case, to match every other surface: the watch
+                            // row is the same label as the phone's, not a different one.
+                            Text("Top")
+                                .font(.system(size: 9, weight: .semibold))
                                 .padding(.horizontal, 4)
                                 .padding(.vertical, 2)
                                 .background(fuel.color.opacity(0.18), in: Capsule())