feat: indicate Costco membership requirement

FuelBoard/ContentView.swift

@@ -1032,6 +1032,12 @@ struct StationRow: View {
                             .background(Capsule().fill(.blue.opacity(0.15)))
                             .foregroundStyle(.blue)
                     }
+                    ForEach(StationNotice.notices(for: station)) { notice in
+                        Image(systemName: notice.symbolName)
+                            .font(.caption2.weight(.semibold))
+                            .foregroundStyle(.secondary)
+                            .accessibilityLabel(notice.title)
+                    }
                 }
                 Text("\(station.address), \(station.postcode)")
                     .font(.caption)

FuelBoard/StationDetailView.swift

@@ -45,6 +45,14 @@ struct StationDetailView: View {
                         LabeledContent("Distance", value: distanceUnit.format(km))
                             .monospacedDigit()
                     }
+                    ForEach(StationNotice.notices(for: station)) { notice in
+                        Label(notice.title, systemImage: notice.symbolName)
+                            .font(.subheadline.weight(.semibold))
+                            .foregroundStyle(.orange)
+                            .padding(.horizontal, 10)
+                            .padding(.vertical, 6)
+                            .background(Capsule().fill(Color.orange.opacity(0.14)))
+                    }
                 }
                 Section {
                     Button {

FuelBoard/StationNotice.swift

@@ -0,0 +1,41 @@
+import Foundation
+
+/// Presentation-only notices derived from existing station metadata.
+///
+/// These do not alter `FuelStation`, persistence, filtering, sorting, or
+/// navigation. They are intentionally small and reusable so additional
+/// informational station notices can be added later from the UI layer.
+enum StationNotice: Identifiable, Equatable {
+    case membershipRequired
+
+    var id: String {
+        switch self {
+        case .membershipRequired: return "membershipRequired"
+        }
+    }
+
+    var title: String {
+        switch self {
+        case .membershipRequired: return "Membership required"
+        }
+    }
+
+    var symbolName: String {
+        switch self {
+        case .membershipRequired: return "creditcard.fill"
+        }
+    }
+
+    static func notices(for station: FuelStation) -> [StationNotice] {
+        isCostco(station) ? [.membershipRequired] : []
+    }
+
+    static func isCostco(_ station: FuelStation) -> Bool {
+        containsCostcoToken(station.brand) || containsCostcoToken(station.name)
+    }
+
+    private static func containsCostcoToken(_ value: String) -> Bool {
+        let tokens = value.uppercased().split { !$0.isLetter && !$0.isNumber }
+        return tokens.contains("COSTCO")
+    }
+}

FuelBoard/en.lproj/Localizable.strings

@@ -148,6 +148,7 @@
 "Done" = "Done";
 "Directions" = "Directions";
 "Report issue" = "Report issue";
+"Membership required" = "Membership required";
 "Report an error?" = "Report an error?";
 "Cancel" = "Cancel";
 "Report" = "Report";