Settings Debug: device coordinates + in-range station indicator

- Debug section now shows the last device fix (lat/lng to 5dp) and its age.
- In-range indicator uses the SAME criteria as live alerts: stations selling
  the monitored fuel within the alert radius of the fix. Green dot + count
  when in range, red when none, grey while waiting for a fix.
- Shows the cheapest in-range station (name, distance, price).
- ProximityMonitor recomputes the snapshot on every location/stations
  change and on Debug-section appear; ContentView passes the live status.
- SettingsView extracted to its own property to keep TabView body within
  the compiler type-check budget. 35 tests pass.

FuelBoard/ContentView.swift

@@ -144,16 +144,7 @@ struct ContentView: View {
             )
             .tabItem { Label("Alerts", systemImage: "bell.fill") }
 
-            SettingsView(
-                distanceUnit: $distanceUnit,
-                alertsFuel: alertsFuel,
-                alertsRadiusKM: alertsRadius,
-                testAlertResult: monitor.lastTestResult,
-                onTestAlert: { monitor.sendTestNotification() },
-                onPlainTestAlert: { monitor.sendPlainTestNotification() },
-                onShowOnboarding: { showOnboarding = true }
-            )
-            .tabItem { Label("Settings", systemImage: "gearshape.fill") }
+            settingsTab
         }
         .fullScreenCover(isPresented: $showOnboarding) {
             OnboardingView {
@@ -255,6 +246,23 @@ struct ContentView: View {
         }
     }
 
+    /// The Settings tab, extracted from `body` so the TabView expression stays
+    /// within the compiler's type-check budget.
+    private var settingsTab: some View {
+        SettingsView(
+            distanceUnit: $distanceUnit,
+            alertsFuel: alertsFuel,
+            alertsRadiusKM: alertsRadius,
+            testAlertResult: monitor.lastTestResult,
+            onTestAlert: { monitor.sendTestNotification() },
+            onPlainTestAlert: { monitor.sendPlainTestNotification() },
+            onRefreshDebugStatus: { monitor.refreshDebugStatus() },
+            onShowOnboarding: { showOnboarding = true },
+            debugStatus: monitor.debugStatus
+        )
+        .tabItem { Label("Settings", systemImage: "gearshape.fill") }
+    }
+
     private func toggleFavourite(_ station: FuelStation, fuel: FuelType) {
         let key = FavouriteEntry(station: station, fuel: fuel)
         if favourites.contains(where: { $0.id == key.id }) {