add upload mode to queue entries to prevent cross-submission

lib/models/pending_upload.dart

@@ -1,10 +1,12 @@
 import 'package:latlong2/latlong.dart';
 import 'camera_profile.dart';
+import '../state/settings_state.dart';
 
 class PendingUpload {
   final LatLng coord;
   final double direction;
   final CameraProfile profile;
+  final UploadMode uploadMode; // Capture upload destination when queued
   final int? originalNodeId; // If this is an edit, the ID of the original OSM node
   int attempts;
   bool error;
@@ -13,6 +15,7 @@ class PendingUpload {
     required this.coord,
     required this.direction,
     required this.profile,
+    required this.uploadMode,
     this.originalNodeId,
     this.attempts = 0,
     this.error = false,
@@ -21,11 +24,24 @@ class PendingUpload {
   // True if this is an edit of an existing camera, false if it's a new camera
   bool get isEdit => originalNodeId != null;
 
+  // Get display name for the upload destination
+  String get uploadModeDisplayName {
+    switch (uploadMode) {
+      case UploadMode.production:
+        return 'Production';
+      case UploadMode.sandbox:
+        return 'Sandbox';
+      case UploadMode.simulate:
+        return 'Simulate';
+    }
+  }
+
   Map<String, dynamic> toJson() => {
         'lat': coord.latitude,
         'lon': coord.longitude,
         'dir': direction,
         'profile': profile.toJson(),
+        'uploadMode': uploadMode.index,
         'originalNodeId': originalNodeId,
         'attempts': attempts,
         'error': error,
@@ -37,6 +53,9 @@ class PendingUpload {
         profile: j['profile'] is Map<String, dynamic>
             ? CameraProfile.fromJson(j['profile'])
             : CameraProfile.genericAlpr(),
+        uploadMode: j['uploadMode'] != null 
+            ? UploadMode.values[j['uploadMode']] 
+            : UploadMode.production, // Default for legacy entries
         originalNodeId: j['originalNodeId'],
         attempts: j['attempts'] ?? 0,
         error: j['error'] ?? false,