Phase 3.6: B+C+D komplett + HealthKit Sync

D.10 401-Handling: APIError.unauthorized, NotificationCenter-Bridge,
  AuthSession.logout() bei 401 → User landet wieder im Login

D.12 PWA-Deep-Links: Settings-Section mit Forum/Hunde/Walks/Settings
  öffnet Safari per https://banyaro.app/#fragment

B.4 Auto-Pause: 2-min-Inaktivität → isAutoPaused, automatischer Resume bei
  nächstem GPS-Update. Settings-Toggle, im UI eigenes Badge "Auto-Pause"
  (grau vs. Pause orange).

C.7 Edit/Delete: RouteUpdateBody + APIClient.patch + APIClient.delete,
  EditRouteSheet (Name/Beschreibung/Public), Menu in Toolbar (nur eigene
  Touren), Alert für Delete.

C.9 Statistik-Tab: neuer Tab "Statistik" zwischen Hunde und Mehr. Filtert
  /api/routes auf meine Touren, rechnet Woche/Monat/Allzeit (Distanz, Dauer,
  Touren), Längste Tour, aktuelle Streak (Tage in Folge).

B.5 Walk-Review: Map-Header an die Spitze des FinishWalkSheet-Forms.

B.6 Geo-Fotos: CapturedPhoto (Data + GPSPoint?), PhotoLocation @Model in
  SwiftData. Kamera während Walk taggt mit tracker.points.last. Nach Upload:
  foto_url aus Response → PhotoLocation persistiert. MiniRouteMap rendert
  Annotations mit Tap-Callback, PhotoViewerSheet zeigt Foto fullscreen.

C.8 Share PNG+GPX: RouteShareImage (MKMapSnapshotter + Polyline overlay +
  SwiftUI ShareCard via ImageRenderer), GPXExporter (Tempfile mit XML),
  ShareSheet (UIActivityViewController-Wrapper), Menu in Route-Toolbar.

D.11 Icon-Varianten: AppIcon-Dark (0.45 Brightness), AppIcon-Tinted
  (Grayscale + Kontrastverstärkung), Contents.json mit appearance entries.

A.2 HealthKit: BanYaroGo.entitlements (com.apple.developer.healthkit),
  NSHealthShare/UpdateUsageDescription. WalkHealthSync.shared mit
  HKWorkoutBuilder (.walking) + HKWorkoutRouteBuilder, Timestamps gleichmäßig
  über Walk-Dauer verteilt. Settings-Toggle mit Permission-Request.

BanYaroGo/Support/GPXExporter.swift

@@ -0,0 +1,47 @@
+import Foundation
+
+enum GPXExporter {
+    /// Writes the route to a temporary `.gpx` file and returns its URL.
+    static func write(detail: RouteDetail) -> URL? {
+        let xml = generate(detail: detail)
+        let safeName = detail.name
+            .replacingOccurrences(of: "/", with: "-")
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+        let filename = safeName.isEmpty ? "tour" : safeName
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent("\(filename).gpx")
+        do {
+            try xml.write(to: url, atomically: true, encoding: .utf8)
+            return url
+        } catch {
+            return nil
+        }
+    }
+
+    static func generate(detail: RouteDetail) -> String {
+        let trkpts = detail.gpsTrack.map { p -> String in
+            if let alt = p.alt {
+                return "      <trkpt lat=\"\(p.lat)\" lon=\"\(p.lon)\"><ele>\(alt)</ele></trkpt>"
+            } else {
+                return "      <trkpt lat=\"\(p.lat)\" lon=\"\(p.lon)\"/>"
+            }
+        }.joined(separator: "\n")
+
+        let safeName = detail.name
+            .replacingOccurrences(of: "&", with: "&amp;")
+            .replacingOccurrences(of: "<", with: "&lt;")
+            .replacingOccurrences(of: ">", with: "&gt;")
+
+        return """
+        <?xml version="1.0" encoding="UTF-8"?>
+        <gpx version="1.1" creator="Ban Yaro Go" xmlns="http://www.topografix.com/GPX/1/1">
+          <trk>
+            <name>\(safeName)</name>
+            <trkseg>
+        \(trkpts)
+            </trkseg>
+          </trk>
+        </gpx>
+        """
+    }
+}