fix: card thumbnail overflow — use GeometryReader to constrain image

Images with .fill were expanding beyond the 180pt frame because
SwiftUI's .clipped() doesn't constrain the layout, only the
rendering. Now uses GeometryReader to set explicit width + height
on the image, then clips the container. Guarantees 180pt max
regardless of image aspect ratio.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ios/Platform/Platform/Features/Reader/Views/EntryListView.swift

@@ -255,10 +255,12 @@ struct EntryCardView: View {
                 AsyncImage(url: thumbURL) { phase in
                     switch phase {
                     case .success(let image):
+                        GeometryReader { geo in
                             image
                                 .resizable()
                                 .aspectRatio(contentMode: .fill)
-                            .frame(maxWidth: .infinity)
+                                .frame(width: geo.size.width, height: 180)
+                        }
                         .frame(height: 180)
                         .clipped()
                     default: