Redesign 3D gallery as single hall per artist with exit navigation.

Restore React client source, add hall-to-hall navigation via painting influences grouped by movement, and update documentation.

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

Documentation/data-and-images.md

@@ -34,6 +34,8 @@ File names are sanitised `{Artist}_{Title}.{ext}`. The image service can redisco
    - Downloads painting images into `paintings/`.
 3. Writes **painting_influences** edges from curated scholarship references.
 
+Those influence edges also power **3D hall navigation**: predecessors and successors at each artist’s exit doorway are computed from this table (see `GET /api/artists/:id/navigation` in [API.md](API.md)).
+
 Artists are grouped by movement and century; the seed list targets at most ~100 artists per century.
 
 ## On-demand image resolution