Settings: move test notifications into hidden Debug section + dev flag

- Test-alert buttons moved out of the Alerts section into a Debug section.
- Debug section only renders when the debug flag is on; completely hidden
  otherwise (no user-facing toggle).
- Hidden toggle: tap Settings → About → Version five times to flip the
  flag (keychain + app-group storage, survives reinstall).
- About section added with version/build number.
- 35 tests pass.

FuelBoard/SettingsView.swift

@@ -3,10 +3,13 @@ import StoreKit
 import UserNotifications
 import WidgetKit
 
-/// Settings tab — distance units, onboarding replay, a tip jar, and
-/// test-alert buttons. The first test button uses REAL data (the actual
-/// cheapest station for the monitored fuel within the radius, exactly like a
-/// live alert) via `onTestAlert`; the second fires with no criteria at all.
+/// Settings tab — distance units, onboarding replay, a tip jar, and an About
+/// section. Test-notification buttons live in a Debug section that is hidden
+/// unless the developer debug flag is on (tap the About → Version row five
+/// times to toggle it — no user-facing switch). The first test button uses
+/// REAL data (the actual cheapest station for the monitored fuel within the
+/// radius, exactly like a live alert) via `onTestAlert`; the second fires
+/// with no criteria at all.
 struct SettingsView: View {
     @Binding var distanceUnit: DistanceUnit
     /// The fuel + radius currently configured for alerts (mirrors the Alerts
@@ -27,6 +30,11 @@ struct SettingsView: View {
     @State private var showTipAlert = false
     @State private var tipAlertMessage = ""
     @State private var testAlertMessage: String?
+    /// Hidden developer flag — the Debug section only appears when on. Toggled
+    /// by tapping the About → Version row five times (NOT a user-facing switch).
+    @State private var debugMode: Bool = FuelStore.loadDebugMode()
+    @State private var versionTapCount = 0
+    @State private var lastVersionTap = Date.distantPast
 
     var body: some View {
         NavigationStack {
@@ -58,31 +66,33 @@ struct SettingsView: View {
                     Text("Replay the welcome screen, including the location and notification permission prompts.")
                 }
 
-                Section {
-                    Button {
-                        sendTestAlert()
-                    } label: {
-                        Label("Test alert notification (real data)", systemImage: "bell.badge.fill")
+                if debugMode {
+                    Section {
+                        Button {
+                            sendTestAlert()
+                        } label: {
+                            Label("Test alert notification (real data)", systemImage: "bell.badge.fill")
+                        }
+                        if let testAlertMessage {
+                            Text(testAlertMessage)
+                                .font(.footnote)
+                                .foregroundStyle(.secondary)
+                        }
+                        if let testAlertResult {
+                            Label(testAlertResult, systemImage: "checkmark.circle.fill")
+                                .font(.footnote)
+                                .foregroundStyle(.green)
+                        }
+                        Button {
+                            onPlainTestAlert()
+                        } label: {
+                            Label("Send plain test notification", systemImage: "bell.slash.fill")
+                        }
+                    } header: {
+                        Text("Debug")
+                    } footer: {
+                        Text("The first button applies the real criteria — cheapest \(alertsFuel.displayName.lowercased()) station within \(distanceUnit.format(alertsRadiusKM)) of you — and sends the actual station's name, price and coordinates. The second fires with no criteria at all (nearest seller), still carrying a real station, just to verify a notification appears and tapping it opens directions.")
                     }
-                    if let testAlertMessage {
-                        Text(testAlertMessage)
-                            .font(.footnote)
-                            .foregroundStyle(.secondary)
-                    }
-                    if let testAlertResult {
-                        Label(testAlertResult, systemImage: "checkmark.circle.fill")
-                            .font(.footnote)
-                            .foregroundStyle(.green)
-                    }
-                    Button {
-                        onPlainTestAlert()
-                    } label: {
-                        Label("Send plain test notification", systemImage: "bell.slash.fill")
-                    }
-                } header: {
-                    Text("Alerts")
-                } footer: {
-                    Text("The first button applies the real criteria — cheapest \(alertsFuel.displayName.lowercased()) station within \(distanceUnit.format(alertsRadiusKM)) of you — and sends the actual station's name, price and coordinates. The second fires with no criteria at all (nearest seller), still carrying a real station, just to verify a notification appears and tapping it opens directions.")
                 }
 
                 Section {
@@ -105,6 +115,22 @@ struct SettingsView: View {
                     Text("A small tip helps keep the data relay and app development going. Thank you!")
                 }
 
+                Section {
+                    HStack {
+                        Text("Version")
+                        Spacer()
+                        Text(appVersion)
+                            .foregroundStyle(.secondary)
+                            .monospacedDigit()
+                            .contentShape(Rectangle())
+                            .onTapGesture { handleVersionTap() }
+                    }
+                } header: {
+                    Text("About")
+                } footer: {
+                    Text("FuelBoard \(appVersion)")
+                }
+
                 if let message = tipStore.message {
                     Section {
                         Text(message)
@@ -120,6 +146,29 @@ struct SettingsView: View {
         }
     }
 
+    private var appVersion: String {
+        let version = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "1.0"
+        let build = Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String ?? "1"
+        return "\(version) (\(build))"
+    }
+
+    /// Hidden debug-mode toggle: five taps on the Version row flips the flag.
+    /// Nothing in the UI advertises this — the Debug section simply appears or
+    /// disappears. Deliberately NOT a visible switch so end users never see it.
+    private func handleVersionTap() {
+        let now = Date()
+        if now.timeIntervalSince(lastVersionTap) > 0.6 {
+            versionTapCount = 0
+        }
+        lastVersionTap = now
+        versionTapCount += 1
+        if versionTapCount >= 5 {
+            versionTapCount = 0
+            debugMode.toggle()
+            FuelStore.saveDebugMode(debugMode)
+        }
+    }
+
     private func sendTestAlert() {
         UNUserNotificationCenter.current().getNotificationSettings { settings in
             Task { @MainActor in