feat: Implement expiring cache for S3 image URLs, add error retry logic, and clear image caches on app startup.

lib/core/utils/image_url_resolver.dart

@@ -1,12 +1,22 @@
 import 'package:real_estate_mobile/core/network/api_client.dart';
 
+class _CachedUrl {
+  final String url;
+  final DateTime cachedAt;
+  _CachedUrl(this.url) : cachedAt = DateTime.now();
+
+  /// Presigned URLs typically expire in 1 hour; refresh after 45 minutes.
+  bool get isExpired =>
+      DateTime.now().difference(cachedAt).inMinutes >= 45;
+}
+
 /// Resolves S3 keys to presigned download URLs via the backend API.
-/// Caches results in memory to avoid repeated API calls.
+/// Caches results in memory with expiry to handle presigned URL expiration.
 class ImageUrlResolver {
   ImageUrlResolver._();
   static final ImageUrlResolver instance = ImageUrlResolver._();
 
-  final Map<String, String> _cache = {};
+  final Map<String, _CachedUrl> _cache = {};
   final Map<String, Future<String?>> _pending = {};
 
   /// Returns a direct image URL.
@@ -18,8 +28,9 @@ class ImageUrlResolver {
       return imageUrl;
     }
 
-    // Check cache
+    // Check cache — only use if not expired
-    if (_cache.containsKey(imageUrl)) return _cache[imageUrl];
+    final cached = _cache[imageUrl];
+    if (cached != null && !cached.isExpired) return cached.url;
 
     // Deduplicate in-flight requests for the same key
     if (_pending.containsKey(imageUrl)) return _pending[imageUrl];
@@ -29,7 +40,7 @@ class ImageUrlResolver {
 
     try {
       final result = await future;
-      if (result != null) _cache[imageUrl] = result;
+      if (result != null) _cache[imageUrl] = _CachedUrl(result);
       return result;
     } finally {
       _pending.remove(imageUrl);

lib/core/widgets/s3_image.dart

@@ -33,6 +33,7 @@ class _S3ImageState extends State<S3Image> {
   String? _resolvedUrl;
   bool _loading = true;
   bool _failed = false;
+  bool _retried = false;
 
   @override
   void initState() {
@@ -106,13 +107,22 @@ class _S3ImageState extends State<S3Image> {
 
     return CachedNetworkImage(
       imageUrl: _resolvedUrl!,
-      cacheKey: widget.imageUrl,
+      cacheKey: widget.imageUrl ?? _resolvedUrl!,
       width: widget.width,
       height: widget.height,
       fit: widget.fit,
       alignment: widget.alignment,
       placeholder: (ctx, _) => _buildPlaceholder(ctx),
-      errorWidget: (ctx, _, _) => _buildError(ctx),
+      errorWidget: (ctx, _, err) {
+        // On error (expired URL), evict and retry once
+        if (!_retried) {
+          _retried = true;
+          ImageUrlResolver.instance.evict(widget.imageUrl);
+          _resolve();
+          return _buildPlaceholder(ctx);
+        }
+        return _buildError(ctx);
+      },
     );
   }
 }

lib/main.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:real_estate_mobile/config/app_config.dart';
 import 'package:real_estate_mobile/config/firebase_config.dart';
 import 'package:real_estate_mobile/core/theme/app_theme.dart';
+import 'package:real_estate_mobile/core/utils/image_url_resolver.dart';
 import 'package:real_estate_mobile/routing/app_router.dart';
 
 Future<void> mainCommon(Flavor flavor) async {
@@ -12,6 +13,11 @@ Future<void> mainCommon(Flavor flavor) async {
 
   await Firebase.initializeApp(options: FirebaseConfig.currentOptions);
 
+  // Clear stale image caches on app start to ensure fresh presigned URLs
+  ImageUrlResolver.instance.clearCache();
+  PaintingBinding.instance.imageCache.clear();
+  PaintingBinding.instance.imageCache.clearLiveImages();
+
   runApp(const ProviderScope(child: MyApp()));
 }