Implement model optimization and caching for 3D characters

- Added a new modelsProxyRouter to handle requests for optimized 3D character models.
- Introduced modelsProxyService to manage GLB file optimization using gltf-transform with Draco compression.
- Updated app.js to include the new modelsProxyRouter for API access.
- Enhanced .gitignore to exclude model cache files.
- Added scripts for optimizing GLB models and updated README with optimization instructions.
- Integrated DRACOLoader in Character3D.vue for loading compressed models.
- Updated FamilyView.vue to streamline character rendering logic.

backend/routers/modelsProxyRouter.js

@@ -0,0 +1,28 @@
+import express from 'express';
+import path from 'path';
+import { getOptimizedModelPath } from '../services/modelsProxyService.js';
+
+const router = express.Router();
+
+/**
+ * GET /api/models/3d/falukant/characters/:filename
+ * Liefert die Draco-optimierte GLB-Datei (aus Cache oder nach Optimierung).
+ */
+router.get('/3d/falukant/characters/:filename', async (req, res) => {
+  const { filename } = req.params;
+
+  try {
+    const cachePath = await getOptimizedModelPath(filename);
+    res.setHeader('Content-Type', 'model/gltf-binary');
+    res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
+    res.sendFile(cachePath);
+  } catch (e) {
+    if (e.message?.includes('Invalid model filename') || e.message?.includes('not found')) {
+      return res.status(404).send(e.message);
+    }
+    console.error('[models-proxy]', e.message);
+    res.status(500).send('Model optimization failed');
+  }
+});
+
+export default router;