fix: collectino post background

internal/repository/post_repo.go

@@ -118,7 +118,7 @@ func (r *PostRepo) FindByID(ctx context.Context, id string) (*model.Post, error)
 		}
 		return nil, fmt.Errorf("find post: %w", err)
 	}
-	imgs, err := r.imagesFor(ctx, []string{p.ID})
+	imgs, err := r.ImagesFor(ctx, []string{p.ID})
 	if err != nil {
 		return nil, err
 	}
@@ -217,7 +217,7 @@ func (r *PostRepo) collectPosts(ctx context.Context, total int, query string, ar
 	}
 
 	if len(ids) > 0 {
-		imgs, err := r.imagesFor(ctx, ids)
+		imgs, err := r.ImagesFor(ctx, ids)
 		if err != nil {
 			return nil, 0, err
 		}
@@ -228,9 +228,12 @@ func (r *PostRepo) collectPosts(ctx context.Context, total int, query string, ar
 	return posts, total, nil
 }
 
-// imagesFor returns a map post_id → [images...] for a batch of post IDs in
-// a single query so we don't N+1 the feed endpoint.
-func (r *PostRepo) imagesFor(ctx context.Context, postIDs []string) (map[string][]model.PostImage, error) {
+// ImagesFor returns a map post_id → [images...] for a batch of post IDs in
+// a single query so we don't N+1 the feed endpoint. Exported because the
+// CollectionService needs to hydrate images onto posts that come back
+// from CollectionRepo.PostsIn (which only joins posts/users — not
+// post_images — to keep that query focused).
+func (r *PostRepo) ImagesFor(ctx context.Context, postIDs []string) (map[string][]model.PostImage, error) {
 	out := make(map[string][]model.PostImage, len(postIDs))
 	if len(postIDs) == 0 {
 		return out, nil