Posters: fetch TheMovieDB images at the shown size, not the original

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/arr/image.go

@@ -35,7 +35,7 @@ func (c *Client) Poster(images []Image, inLibrary bool) (key string, fetch func(
 				if err != nil && remote != "" {
 					// The instance has no usable copy (not cached, or behind a login):
 					// use the metadata provider's, as for titles not in the library.
-					if remoteData, remoteErr := FetchURL(ctx, remote); remoteErr == nil {
+					if remoteData, remoteErr := FetchURL(ctx, tmdbSized(remote, large)); remoteErr == nil {
 						return remoteData, nil
 					}
 				}
@@ -44,7 +44,9 @@ func (c *Client) Poster(images []Image, inLibrary bool) (key string, fetch func(
 		}
 		if img.RemoteURL != "" {
 			remote := img.RemoteURL
-			return remote, func(ctx context.Context, _ bool) ([]byte, error) { return FetchURL(ctx, remote) }, true
+			return remote, func(ctx context.Context, large bool) ([]byte, error) {
+				return FetchURL(ctx, tmdbSized(remote, large))
+			}, true
 		}
 	}
 	return "", nil, false
@@ -84,6 +86,24 @@ func (c *Client) localPoster(ctx context.Context, local string, large bool) ([]b
 	return try(local)
 }
 
+// tmdbSized asks TheMovieDB for a poster of the size that is shown instead of
+// the original Radarr hands out (often 2000×3000 and over 2 MB, which takes
+// longer to download and to decode than everything else together): 780
+// pixels wide for real images, 342 for block characters. Other URLs are
+// returned as they are.
+func tmdbSized(rawURL string, large bool) string {
+	u, err := url.Parse(rawURL)
+	if err != nil || u.Host != "image.tmdb.org" || !strings.HasPrefix(u.Path, "/t/p/original/") {
+		return rawURL
+	}
+	size := "w342"
+	if large {
+		size = "w780"
+	}
+	u.Path = "/t/p/" + size + strings.TrimPrefix(u.Path, "/t/p/original")
+	return u.String()
+}
+
 // scaledVariant turns /MediaCover/1/poster.jpg?x into
 // /MediaCover/1/poster-250.jpg?x (for width 250; Radarr and Sonarr keep 250
 // and 500).