fix: image transforms via Sharp, model photos crash, video duration

- Backend: add Sharp image transform endpoint (/assets/:id?transform=X)
  with presets: mini(64), thumbnail(200), preview(480), medium(960), banner(1280)
  Transformed images are cached as webp next to originals
- Frontend: fix model photos crash (p.directus_files_id → p)
- Frontend: fix model banner URL (data.model.banner.id → data.model.banner)
- Frontend: fix video duration display (video.movie.duration → video.movie_file?.duration)
  across models/[slug], videos, videos/[slug], and home pages

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/routes/videos/[slug]/+page.svelte

@@ -221,7 +221,7 @@ let showPlayer = $state(false);
               <div
                 class="absolute bottom-4 left-4 bg-black/70 text-white px-3 py-1 rounded font-medium"
               >
-                {formatVideoDuration(data.video.movie.duration)}
+                {#if data.video.movie_file?.duration}{formatVideoDuration(data.video.movie_file.duration)}{/if}
               </div>
               {#if data.video.premium}
                 <div