fix(falukant): revalidate replaced character meshes

backend/routers/modelsProxyRouter.js

@@ -14,7 +14,10 @@ router.get('/3d/falukant/characters/:filename', async (req, res) => {
   try {
     const cachePath = await getOptimizedModelPath(filename);
     res.setHeader('Content-Type', 'model/gltf-binary');
-    res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
+    // GLB files can be replaced under the same filename during an asset deploy.
+    // Revalidate cached copies so clients receive a changed mesh without needing
+    // to clear their browser cache.
+    res.setHeader('Cache-Control', 'public, max-age=0, must-revalidate');
     res.sendFile(cachePath);
   } catch (e) {
     if (e.message?.includes('Invalid model filename') || e.message?.includes('not found')) {