feat(home): tap opens detail, long-press plays from home cards

Home carousel cards route a tap to the item's detail / Episode Focus
View and a ~500ms long-press to a confirm-then-play flow. MediaCard gains
an onLongPress prop with pointer-based detection (cancelled on >10px move
so carousel scroll is unaffected, trailing click suppressed). Episode
taps route to /library/<seriesId>?episode=<id>; the bare-episode detail
page links back to its parent series/season.

TRACES: UR-058 | DR-087

src/lib/components/home/Carousel.svelte

@@ -7,10 +7,11 @@
     title: string;
     items: MediaItem[];
     onItemClick?: (item: MediaItem) => void;
+    onItemLongPress?: (item: MediaItem) => void;
     showAll?: () => void;
   }
 
-  let { title, items, onItemClick, showAll }: Props = $props();
+  let { title, items, onItemClick, onItemLongPress, showAll }: Props = $props();
 
   let scrollContainer: HTMLDivElement | null = $state(null);
   let showLeftArrow = $state(false);
@@ -60,6 +61,7 @@
           size="medium"
           showProgress={true}
           onclick={() => onItemClick?.(item)}
+          onLongPress={onItemLongPress ? () => onItemLongPress(item) : undefined}
         />
       {/each}
     </div>