Siri: cheapest [fuel] near me intent + App Shortcuts (cached-first, freshness label)

Shared/SiriCheapestLookup.swift

@@ -0,0 +1,54 @@
+import Foundation
+
+/// Pure, testable logic behind the Siri "cheapest fuel near me" intent.
+/// Foundation-only on purpose: `Shared/` joins both the app and widget
+/// targets, and FuelBoardTests exercises this directly.
+enum SiriCheapestLookup {
+
+    /// The cheapest station selling `fuel`, tie-broken by distance from the
+    /// given point. Stations without a price for `fuel` are skipped entirely.
+    /// Returns nil when no station sells the fuel.
+    static func cheapest(
+        in stations: [FuelStation],
+        fuel: FuelType,
+        fromLat lat: Double,
+        lng: Double
+    ) -> FuelStation? {
+        stations
+            .filter { $0.prices[fuel] != nil }
+            .min { lhs, rhs in
+                guard let lp = lhs.prices[fuel], let rp = rhs.prices[fuel] else {
+                    return false
+                }
+                if lp != rp { return lp < rp }
+                return lhs.distanceKM(to: lat, lng2: lng) < rhs.distanceKM(to: lat, lng2: lng)
+            }
+    }
+
+    /// A short freshness stamp for the dialog: "as of 6:30 AM".
+    /// Prefers the GOV.UK `data_updated` stamp carried by the relay (ISO 8601
+    /// with or without fractional seconds); falls back to the local
+    /// last-refresh date; returns "" when there is no data at all.
+    static func freshnessLabel(updated: String?, lastRefresh: Date?, now: Date = Date()) -> String {
+        let date: Date?
+        if let updated {
+            date = Self.parseISO(updated) ?? lastRefresh
+        } else {
+            date = lastRefresh
+        }
+        guard let date else { return "" }
+        let formatter = DateFormatter()
+        formatter.dateFormat = "h:mm a"
+        formatter.locale = Locale(identifier: "en_GB")
+        return "as of \(formatter.string(from: date))"
+    }
+
+    private static func parseISO(_ string: String) -> Date? {
+        let withFraction = ISO8601DateFormatter()
+        withFraction.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        if let date = withFraction.date(from: string) { return date }
+        let plain = ISO8601DateFormatter()
+        plain.formatOptions = [.withInternetDateTime]
+        return plain.date(from: string)
+    }
+}