Backlog, tests, logo compression, security audit, App Store icon

- BACKLOG.md: P0-P3 roadmap incl. govuk API switch (blocked on credentials)
- APPSTORE.md: review-gate analysis (2 blockers: LAN data source, Always-location notes)
- SECURITY.md: audit - no secrets, no ATS holes, one MEDIUM (relay IP in binary, planned fix)
- FuelBoardTests/: SPM package, 28 tests on real Shared/ sources (sanitizer, price guard, RAG, sort, distance, brands)
- Logos: proper 2x/3x pairs, palette-quantized, 75% smaller (315KB -> 79KB)
- App icon: 1024px fuelpump on gradient (was missing entirely -> instant rejection)
- decodeStations(from:) exposed for testability; relay fetch reuses it

Shared/FuelPriceProvider.swift

@@ -22,6 +22,25 @@ enum FuelPriceProvider {
     /// Default: the keyless relay (full-UK Fuel Finder data). Falls back to
     /// the England-wide sample set when the relay is unreachable.
     static let active: FuelPriceProviding = RelayFuelProvider()
+
+    /// Decodes a relay payload into stations, applying the defensive price
+    /// band. Internal so the unit-test target can exercise the guard.
+    static func decodeStations(from data: Data) throws -> [FuelStation] {
+        let payload = try JSONDecoder().decode(RelayResponse.self, from: data)
+        return payload.stations.map { relay in
+            FuelStation(
+                id: relay.id ?? relay.name ?? UUID().uuidString,
+                name: (relay.name ?? "Unknown").sanitizedStationTitle,
+                brand: relay.brand ?? "",
+                address: relay.address ?? "",
+                postcode: relay.postcode ?? "",
+                lat: relay.lat ?? 0,
+                lng: relay.lng ?? 0,
+                prices: relay.allPrices,
+                priceUpdated: nil
+            )
+        }
+    }
 }
 
 // MARK: - Relay provider (default)
@@ -54,20 +73,7 @@ struct RelayFuelProvider: FuelPriceProviding {
         guard let http = response as? HTTPURLResponse, http.statusCode == 200 else {
             throw FuelProviderError.relayUnavailable
         }
-        let payload = try JSONDecoder().decode(RelayResponse.self, from: data)
-        return payload.stations.map { relay in
-            FuelStation(
-                id: relay.id ?? relay.name ?? UUID().uuidString,
-                name: (relay.name ?? "Unknown").sanitizedStationTitle,
-                brand: relay.brand ?? "",
-                address: relay.address ?? "",
-                postcode: relay.postcode ?? "",
-                lat: relay.lat ?? 0,
-                lng: relay.lng ?? 0,
-                prices: relay.allPrices,
-                priceUpdated: nil
-            )
-        }
+        return try FuelPriceProvider.decodeStations(from: data)
     }
 }