Fix iframe recursion and remove all localStorage/cookies site-wide

- Add target="_top" to all ← SPACE / back-to-root links so navigating
  back to index.html breaks out of the content iframe instead of loading
  it recursively inside itself (Images, Music, Watchlists hubs)
- Remove all localStorage usage: visited-star tracking in index.html
  (resets each visit, no persistence without storage), and lightbox
  "show once" guards in all section pages (lightboxes now show on every
  load — Videos, Watchlists, Music). build.py templates updated so
  future generated pages stay clean.

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

Watchlists/watchlist-template.html

@@ -447,10 +447,7 @@
 
             // Lightbox: show on first load
             const lightbox = document.getElementById('lightbox');
-            if (!localStorage.getItem('watchlist-caa-seen')) {
-                lightbox.style.display = 'flex';
-                localStorage.setItem('watchlist-caa-seen', '1');
-            }
+            lightbox.style.display = 'flex';
 
             function closeLightbox() {
                 lightbox.style.display = 'none';