Settings: plain test notification + foreground banner delegate

- New 'Send plain test notification' button fires with zero criteria checks
  (no geofence, no cheapest check, no permission gate) to isolate delivery
  and tap behaviour
- ProximityMonitor is now the UNUserNotificationCenter delegate: banners
  show even in the foreground (system suppresses them otherwise), and taps
  complete the 'open FuelBoard' action

FuelBoard/ProximityMonitor.swift

@@ -8,7 +8,7 @@ import SwiftUI
 /// Region budget: iOS allows 20 monitored regions per app — favourites are
 /// always registered first, then the closest remaining stations fill the rest.
 @MainActor
-final class ProximityMonitor: NSObject, ObservableObject, @preconcurrency CLLocationManagerDelegate {
+final class ProximityMonitor: NSObject, ObservableObject, @preconcurrency CLLocationManagerDelegate, UNUserNotificationCenterDelegate {
     @Published var monitoredStationIDs: [String] = []
     @Published var lastAlert: String?
 
@@ -25,6 +25,9 @@ final class ProximityMonitor: NSObject, ObservableObject, @preconcurrency CLLoca
         manager.delegate = self
         manager.desiredAccuracy = kCLLocationAccuracyHundredMeters
         manager.pausesLocationUpdatesAutomatically = true
+        // Show alert banners even while the app is open, and complete the tap
+        // action (opening FuelBoard) when the user taps a notification.
+        UNUserNotificationCenter.current().delegate = self
         // Restore persisted state on background relaunch so region events work
         // even before the view fully appears.
         enabled = FuelStore.loadAlertsEnabled()
@@ -187,4 +190,43 @@ final class ProximityMonitor: NSObject, ObservableObject, @preconcurrency CLLoca
         let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: nil)
         UNUserNotificationCenter.current().add(request)
     }
+
+    /// Fires a notification with NO criteria checks at all — no geofence, no
+    /// cheapest-within-radius, no dedup, no permission gate, no fuel/radius
+    /// coupling. Purely tests "does a notification appear, and does tapping
+    /// it open the app". If notifications are denied system-wide nothing can
+    /// display, but this fires regardless of every FuelBoard condition.
+    static func sendPlainTestNotification() {
+        let content = UNMutableNotificationContent()
+        content.title = "FuelBoard test notification"
+        content.body = "This is a plain test alert — no criteria were checked. Tap to open FuelBoard."
+        content.sound = .default
+
+        let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: nil)
+        UNUserNotificationCenter.current().add(request)
+    }
+
+    // MARK: - Notification presentation + tap
+
+    /// Show alert banners even while FuelBoard is in the foreground — without
+    /// this, the system silently suppresses notifications when the app is open.
+    nonisolated func userNotificationCenter(
+        _ center: UNUserNotificationCenter,
+        willPresent notification: UNNotification,
+        withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void
+    ) {
+        Task { @MainActor in
+            completionHandler([.banner, .sound])
+        }
+    }
+
+    /// Tapping a notification just opens the app (the alert's "Tap to open").
+    /// No extra routing — the app comes to the foreground as-is.
+    nonisolated func userNotificationCenter(
+        _ center: UNUserNotificationCenter,
+        didReceive response: UNNotificationResponse,
+        withCompletionHandler completionHandler: @escaping () -> Void
+    ) {
+        completionHandler()
+    }
 }