fix(world): restore shadow auto-update

Reverts the manual shadow refresh throttle introduced in 6d58b90 which
prevented shadows from rendering. Renderer and sun shadow now use
autoUpdate=true and a per-frame needsUpdate=true pulse, matching the
behaviour that produced visible shadows before that commit.

src/pages/page.tsx

@@ -130,7 +130,7 @@ export function HomePage(): React.JSX.Element | null {
 
       gl.shadowMap.enabled = true;
       gl.shadowMap.type = THREE.PCFShadowMap;
-      gl.shadowMap.autoUpdate = false;
+      gl.shadowMap.autoUpdate = true;
       gl.shadowMap.needsUpdate = true;
 
       // The browser hands us a WEBGL_lose_context extension we can use to
@@ -148,7 +148,7 @@ export function HomePage(): React.JSX.Element | null {
       const handleContextRestored = () => {
         gl.shadowMap.enabled = true;
         gl.shadowMap.type = THREE.PCFShadowMap;
-        gl.shadowMap.autoUpdate = false;
+        gl.shadowMap.autoUpdate = true;
         gl.shadowMap.needsUpdate = true;
         logger.info("WebGL", "Context restored");
       };