tag node -> add node, better element offsets, fix splash background on iOS

lib/widgets/download_area_dialog.dart

@@ -64,6 +64,9 @@ class _DownloadAreaDialogState extends State<DownloadAreaDialog> {
     final nTiles = computeTileList(bounds, minZoom, maxZoom).length;
     final totalMb = (nTiles * kTileEstimateKb) / 1024.0;
     
+    // Debug logging to check calculation
+    debugPrint('[DownloadDialog] Tiles: $nTiles, EstimateKb: $kTileEstimateKb, Total MB: $totalMb');
+    
     setState(() {
       _minZoom = minZoom;
       _maxPossibleZoom = maxPossibleZoom;

lib/widgets/map/map_overlays.dart

@@ -57,10 +57,10 @@ class MapOverlays extends StatelessWidget {
             ),
           ),
 
-        // Zoom indicator, positioned above scale bar
+        // Zoom indicator, positioned relative to button bar
         Positioned(
           left: 10,
-          bottom: kZoomIndicatorBottomOffset,
+          bottom: bottomPositionFromButtonBar(kZoomIndicatorSpacingAboveButtonBar, MediaQuery.of(context).padding.bottom),
           child: Container(
             padding: const EdgeInsets.symmetric(horizontal: 7, vertical: 2),
             decoration: BoxDecoration(
@@ -83,10 +83,10 @@ class MapOverlays extends StatelessWidget {
           ),
         ),
 
-        // Attribution overlay
+        // Attribution overlay, positioned relative to button bar
         if (attribution != null)
           Positioned(
-            bottom: kAttributionBottomOffset,
+            bottom: bottomPositionFromButtonBar(kAttributionSpacingAboveButtonBar, MediaQuery.of(context).padding.bottom),
             left: 10,
             child: Container(
               decoration: BoxDecoration(
@@ -104,9 +104,9 @@ class MapOverlays extends StatelessWidget {
             ),
           ),
 
-        // Zoom and layer controls (bottom-right)
+        // Zoom and layer controls (bottom-right), positioned relative to button bar
         Positioned(
-          bottom: 80,
+          bottom: bottomPositionFromButtonBar(kZoomControlsSpacingAboveButtonBar, MediaQuery.of(context).padding.bottom),
           right: 16,
           child: Column(
             children: [

lib/widgets/map_view.dart

@@ -332,10 +332,13 @@ class MapViewState extends State<MapView> {
               selectedTileType: appState.selectedTileType,
             ),
             cameraLayers,
-            // Built-in scale bar from flutter_map 
+            // Built-in scale bar from flutter_map, positioned relative to button bar
             Scalebar(
               alignment: Alignment.bottomLeft,
-              padding: EdgeInsets.only(left: 8, bottom: kScaleBarBottomOffset), // from dev_config
+              padding: EdgeInsets.only(
+                left: 8, 
+                bottom: bottomPositionFromButtonBar(kScaleBarSpacingAboveButtonBar, MediaQuery.of(context).padding.bottom)
+              ),
               textStyle: TextStyle(color: Colors.black, fontWeight: FontWeight.bold),
               lineColor: Colors.black,
               strokeWidth: 3,