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").

FuelBoard/CapsuleStyles.swift

@@ -0,0 +1,155 @@
+import SwiftUI
+
+/// One semantic capsule tone: a foreground and a background for each appearance.
+///
+/// The palette is deliberately a TINTED pair rather than a saturated solid. Every
+/// tone below clears 4.5:1 for its own foreground on its own background in BOTH
+/// appearances (measured, 4.96:1 to 6.72:1), which is what lets one component
+/// carry the same meaning on a white row and a dark card without a second
+/// colour per status.
+///
+/// The pairs are resolved through `UIColor`'s dynamic provider rather than
+/// SwiftUI's `@Environment(\.colorScheme)`: a capsule inside a `List` is often
+/// re-rendered without its body being rebuilt, so a scheme read at body time can
+/// lag one switch behind. This way the colour itself follows the appearance.
+struct CapsuleTone: Equatable {
+    let lightForeground: Color
+    let lightBackground: Color
+    let darkForeground: Color
+    let darkBackground: Color
+
+    var foreground: Color { dynamic(light: lightForeground, dark: darkForeground) }
+    var background: Color { dynamic(light: lightBackground, dark: darkBackground) }
+
+    private func dynamic(light: Color, dark: Color) -> Color {
+        let lightUI = UIColor(light)
+        let darkUI = UIColor(dark)
+        return Color(UIColor { traits in
+            traits.userInterfaceStyle == .dark ? darkUI : lightUI
+        })
+    }
+}
+
+extension CapsuleTone {
+    /// Green: a financial saving.
+    static let saves = CapsuleTone(
+        lightForeground: Color(hex: 0x176B3D), lightBackground: Color(hex: 0xDDF3E5),
+        darkForeground: Color(hex: 0x66D69A), darkBackground: Color(hex: 0x204333)
+    )
+
+    /// Grey: a neutral outcome, neither saving nor costing.
+    static let breakEven = CapsuleTone(
+        lightForeground: Color(hex: 0x555B64), lightBackground: Color(hex: 0xE9EAED),
+        darkForeground: Color(hex: 0xD0D0D5), darkBackground: Color(hex: 0x404044)
+    )
+
+    /// Red: an additional cost.
+    static let costs = CapsuleTone(
+        lightForeground: Color(hex: 0xA63F3D), lightBackground: Color(hex: 0xF9E1DF),
+        darkForeground: Color(hex: 0xEF9690), darkBackground: Color(hex: 0x4B3032)
+    )
+
+    /// Purple: best overall value after travel.
+    static let bestValue = CapsuleTone(
+        lightForeground: Color(hex: 0x7043A1), lightBackground: Color(hex: 0xEEE4F8),
+        darkForeground: Color(hex: 0xD1B4FA), darkBackground: Color(hex: 0x44354F)
+    )
+
+    /// Blue: the lowest fuel price in range.
+    static let cheapest = CapsuleTone(
+        lightForeground: Color(hex: 0x225F9B), lightBackground: Color(hex: 0xE0EFFB),
+        darkForeground: Color(hex: 0x8BC5FA), darkBackground: Color(hex: 0x293F53)
+    )
+
+    /// Neutral grey: proximity. Same family as `breakEven` — both mean "no
+    /// judgement" — but kept as its own pair so proximity and a break-even
+    /// verdict stay independently tunable.
+    static let closestStation = CapsuleTone(
+        lightForeground: Color(hex: 0x525967), lightBackground: Color(hex: 0xE8EAF0),
+        darkForeground: Color(hex: 0xC0C3CC), darkBackground: Color(hex: 0x424349)
+    )
+
+    /// Blue, like `cheapest`: the top favourite IS the cheapest favourite, so it
+    /// must not read as a different class of thing.
+    static let top = CapsuleTone(
+        lightForeground: Color(hex: 0x225F9B), lightBackground: Color(hex: 0xE0EFFB),
+        darkForeground: Color(hex: 0x8BC5FA), darkBackground: Color(hex: 0x293F53)
+    )
+}
+
+/// The one shape rule every capsule in the app follows.
+///
+/// A capsule while the content is a single line; a rounded rectangle once it
+/// wraps. A pill's semicircular ends crowd the text corners at two lines or
+/// more, while a 10pt radius does not. The shape follows what the content
+/// actually DREW, not how many lines it declared, because a label can wrap in a
+/// narrow column without the data changing — "Closest station" is the case that
+/// forced this: one declared line that wraps to two in the listing's price
+/// column.
+///
+/// Measuring happens on the content BEFORE padding, so the drawn line count is
+/// never inflated by the capsule's own insets.
+struct AdaptiveCapsule<Content: View>: View {
+    /// The tone's background fill. The caller resolves it from its own semantics.
+    let fill: Color
+    /// One line's height for the content's font, already scaled with Dynamic
+    /// Type — pass a `@ScaledMetric` so the division below tracks the user's size.
+    let lineHeight: CGFloat
+    /// Lines the content declares, used for the first layout pass before a
+    /// measured height exists.
+    var declaredLineCount: Int = 1
+    var cornerRadius: CGFloat = 10
+    var horizontalPadding: CGFloat
+    var verticalPadding: CGFloat
+    @ViewBuilder let content: Content
+
+    @State private var drawnHeight: CGFloat = 0
+
+    private var lineCount: Int {
+        guard drawnHeight > 0, lineHeight > 0 else { return max(1, declaredLineCount) }
+        return max(1, Int((drawnHeight / lineHeight).rounded()))
+    }
+
+    private var shape: AnyShape {
+        lineCount > 1
+            ? AnyShape(RoundedRectangle(cornerRadius: cornerRadius, style: .continuous))
+            : AnyShape(Capsule())
+    }
+
+    var body: some View {
+        content
+            .background(
+                GeometryReader { proxy in
+                    Color.clear.preference(key: CapsuleContentHeightKey.self,
+                                           value: proxy.size.height)
+                }
+            )
+            .padding(.horizontal, horizontalPadding)
+            .padding(.vertical, verticalPadding)
+            .background(shape.fill(fill))
+            .onPreferenceChange(CapsuleContentHeightKey.self) { drawnHeight = $0 }
+    }
+}
+
+/// Carries the drawn height of a capsule's content up to `lineCount`.
+private struct CapsuleContentHeightKey: PreferenceKey {
+    static let defaultValue: CGFloat = 0
+    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
+        value = max(value, nextValue())
+    }
+}
+
+extension Color {
+    /// A fixed sRGB colour from a 24-bit literal. The capsule palette is
+    /// appearance-specific and supplied per tone, so these are deliberately NOT
+    /// dynamic — `CapsuleTone` resolves the pair itself.
+    init(hex: UInt32) {
+        self.init(
+            .sRGB,
+            red: Double((hex >> 16) & 0xFF) / 255,
+            green: Double((hex >> 8) & 0xFF) / 255,
+            blue: Double(hex & 0xFF) / 255,
+            opacity: 1
+        )
+    }
+}