Cleaned up code, implemented message queue to notify subscribers of document updates.

lib/core/widgets/shimmer_placeholder.dart

@@ -0,0 +1,21 @@
+import 'package:flutter/material.dart';
+import 'package:shimmer/shimmer.dart';
+
+class ShimmerPlaceholder extends StatelessWidget {
+  final Widget child;
+
+  const ShimmerPlaceholder({super.key, required this.child});
+
+  @override
+  Widget build(BuildContext context) {
+    return Shimmer.fromColors(
+      baseColor: Theme.of(context).brightness == Brightness.light
+          ? Colors.grey[300]!
+          : Colors.grey[900]!,
+      highlightColor: Theme.of(context).brightness == Brightness.light
+          ? Colors.grey[100]!
+          : Colors.grey[600]!,
+      child: child,
+    );
+  }
+}