4wswt4ex2: Add like and unlike for post cards

src/lib/feed-model.ts

@@ -18,6 +18,8 @@ export interface CardPost {
   time: number;
   text: string;
   likesCount: number;
+  /** Whether the signed-in person has liked the post. */
+  isLiked: boolean;
   commentsCount: number;
   media: CardMedia[];
 }
@@ -99,6 +101,7 @@ export function toCardPost(item: unknown, index = 0): CardPost | null {
     time: Number.isFinite(t) ? t : Number.NEGATIVE_INFINITY,
     text: typeof post.content === "string" ? post.content : "",
     likesCount: num(item.likesCount ?? post.likesCount),
+    isLiked: post.isLiked === true || item.isLiked === true,
     commentsCount: num(item.commentsCount ?? post.commentsCount),
     media: toMedia(post.mediaItems),
   };