ensure bottom bar is below the metadata panel - move the bottom bar from bottomNavigationBar into the Stack

mobile/lib/presentation/widgets/asset_viewer/asset_viewer.page.dart

@@ -695,15 +695,19 @@ class _AssetViewerState extends ConsumerState<AssetViewer> {
               backgroundDecoration: BoxDecoration(color: backgroundColor),
               enablePanAlways: true,
             ),
-          ],
-        ),
-        bottomNavigationBar: showingBottomSheet
-            ? const SizedBox.shrink()
-            : const Column(
+            if (!showingBottomSheet)
+              Positioned(
+                bottom: 0,
+                left: 0,
+                right: 0,
+                child: Column(
                   mainAxisSize: MainAxisSize.min,
                   mainAxisAlignment: MainAxisAlignment.end,
                   crossAxisAlignment: CrossAxisAlignment.stretch,
-                children: [AssetStackRow(), ViewerBottomBar()],
+                  children: [const AssetStackRow(), const ViewerBottomBar()],
+                ),
+              ),
+          ],
         ),
       ),
     );