add macOS support for ad loading and improve timestamp handling

lib/widgets/ad_banner.dart

@@ -1,3 +1,4 @@
+import "dart:io" show Platform;
 import "package:flutter/foundation.dart" show kIsWeb;
 import "package:flutter/widgets.dart";
 import "package:shadcn_flutter/shadcn_flutter.dart";
@@ -15,11 +16,19 @@ class AdBanner extends StatefulWidget {
 class _AdBannerState extends State<AdBanner> {
   late AdService _adService;
   bool _isLoading = true;
+  bool _isMacOS = false;
 
   @override
   void initState() {
     super.initState();
-    _initializeAds();
+
+    // check if running on macOS
+    if (!kIsWeb && Platform.isMacOS) {
+      _isMacOS = true;
+      _isLoading = false;
+    } else {
+      _initializeAds();
+    }
   }
 
   Future<void> _initializeAds() async {
@@ -46,12 +55,42 @@ class _AdBannerState extends State<AdBanner> {
 
   @override
   void dispose() {
-    _adService.dispose();
+    if (!_isMacOS) {
+      _adService.dispose();
+    }
     super.dispose();
   }
 
   @override
   Widget build(BuildContext context) {
+
+    // Check if we're on mobile (iOS/Android)
+    bool isMobile = !kIsWeb && !_isMacOS && (Platform.isIOS || Platform.isAndroid);
+
+    // Show placeholder only on macOS and web when ads fail to load
+    // On mobile, we want real ads or nothing
+    if (_isMacOS || (!isMobile && !_isLoading && !_adService.isLoaded)) {
+      return ConstrainedBox(
+        constraints: const BoxConstraints(
+          minHeight: 80,
+        ),
+        child: OutlinedContainer(
+          child: Center(
+            child: Text(
+              "ADVERTISEMENT SPACE",
+              style: TextStyle(
+                color: Theme.of(context).colorScheme.mutedForeground,
+                fontSize: 12,
+                fontWeight: FontWeight.w500,
+              ),
+            ),
+          ),
+        ),
+      ).withPadding(
+        horizontal: 8
+      );
+    }
+
     if (_isLoading) {
       return SizedBox(
         height: 50,
@@ -65,11 +104,6 @@ class _AdBannerState extends State<AdBanner> {
       );
     }
 
-    if (!_adService.isLoaded) {
-      // Ad failed to load, show nothing
-      return SizedBox.shrink();
-    }
-
     return _adService.getBannerWidget();
   }
 }