Improve 3D gallery UX, placeholders, and image accuracy.

Add multi-row dynamic halls, eye-level camera, canvas covers for missing works, preserved view when returning from detail, and corrected image overrides for Kauffman and Raphael. Update documentation and add fetched painting assets.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/pages/HomePage.css

@@ -3,6 +3,20 @@
   background: linear-gradient(180deg, #0f0f1a 0%, #1a1a2e 40%, #16213e 100%);
 }
 
+.gallery-session-suspended {
+  position: fixed;
+  inset: 0;
+  z-index: 0;
+  visibility: hidden;
+  pointer-events: none;
+}
+
+.home-overlay {
+  position: relative;
+  z-index: 10;
+  min-height: 100vh;
+}
+
 .site-header {
   text-align: center;
   padding: 24px 16px 8px;