Real-image posters of library titles: use the 500 px copy

Library titles fetched Radarr's/Sonarr's 250×375 poster copy, which
real images show at up to 640 pixels, so movie posters looked soft next
to series posters that came from the provider's full-size original
(Sonarr behind a login). With real images the 500×750 copy is used;
block-character posters keep the small one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019reK4DUGYqDUjniWYJvwUW

internal/ui/cover.go

@@ -468,7 +468,7 @@ func (c *coverView) build(cols, rows int) []styledCell {
 // coverRef says where a poster comes from. The zero value means "no poster".
 type coverRef struct {
 	key   string // identifies the poster in the cache
-	fetch func(ctx context.Context) ([]byte, error)
+	fetch func(ctx context.Context, large bool) ([]byte, error) // large: for real images
 }
 
 // coverFor builds the poster reference of a title from its image list.
@@ -516,6 +516,7 @@ func (a *App) loadCover(ref coverRef, done func(*image.RGBA, error)) {
 	}
 	c.waiting[ref.key] = []func(*image.RGBA, error){done}
 	maxHeight := a.coverMaxHeight()
+	large := a.gfx != nil // real images show the poster at full resolution
 
 	go func() {
 		c.slots <- struct{}{}
@@ -523,7 +524,7 @@ func (a *App) loadCover(ref coverRef, done func(*image.RGBA, error)) {
 		ctx, cancel := context.WithTimeout(context.Background(), 25*time.Second)
 		defer cancel()
 		var img *image.RGBA
-		data, err := ref.fetch(ctx)
+		data, err := ref.fetch(ctx, large)
 		if err == nil {
 			img, err = decodeCover(data, maxHeight)
 		}