Any shader family as the 3D model backdrop

The uber-shader pass is now reusable (_renderUber): choosing 'fam:<i>'
in the Sfondo Modello 3D selector renders that family first (tinted with
the active preset's palette/hue/sat) and overlays the model on top. The
selector lists every family except fluids (already explicit options),
interactive and Modello 3D itself.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/control.html

@@ -139,6 +139,7 @@
           <option value="ring">Fluido Anello</option>
           <option value="vortex">Fluido Vortici</option>
           <option value="wave">Fluido Onda</option>
+          <!-- tutte le altre famiglie vengono aggiunte da control.js -->
         </select>
       </section>