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>

Music/build.py

@@ -99,10 +99,7 @@ def build_lightbox_html(text: str, slug: str) -> tuple[str, str]:
 
     js = f"""
             const lightbox = document.getElementById('lightbox');
-            if (!localStorage.getItem('music-{slug}-seen')) {{
-                lightbox.style.display = 'flex';
-                localStorage.setItem('music-{slug}-seen', '1');
-            }}
+            lightbox.style.display = 'flex';
             const closeLightbox = () => {{ lightbox.style.display = 'none'; }};
             lightbox.addEventListener('click', (e) => {{
                 if (e.target === lightbox) closeLightbox();