Enhance model path handling in modelsProxyService.js

- Refactored model source directory logic to dynamically select between production and local paths.
- Updated error messages to provide clearer context on model source lookup failures.
- Added package-lock.json to .gitignore to streamline dependency management.

backend/services/modelsProxyService.js

@@ -11,10 +11,17 @@ import { spawn } from 'child_process';
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 const BACKEND_DIR = path.join(__dirname, '..');
 const PROJECT_ROOT = path.join(BACKEND_DIR, '..');
-const SOURCE_DIR = path.join(PROJECT_ROOT, 'frontend', 'public', 'models', '3d', 'falukant', 'characters');
+const MODELS_REL = path.join('models', '3d', 'falukant', 'characters');
+const DIST_MODELS = path.join(PROJECT_ROOT, 'frontend', 'dist', MODELS_REL);
+const PUBLIC_MODELS = path.join(PROJECT_ROOT, 'frontend', 'public', MODELS_REL);
 const CACHE_DIR = path.join(BACKEND_DIR, 'data', 'model-cache');
 const CLI_PATH = path.join(BACKEND_DIR, 'node_modules', '.bin', 'gltf-transform');
 
+/** Production: frontend/dist; Local: frontend/public. Ermittelt bei Bedarf. */
+function getSourceDir() {
+  return fs.existsSync(DIST_MODELS) ? DIST_MODELS : PUBLIC_MODELS;
+}
+
 /** Erlaubte Dateinamen (nur [a-z0-9_.-]+.glb) */
 const FILENAME_RE = /^[a-z0-9_.-]+\.glb$/i;
 
@@ -80,12 +87,13 @@ export async function getOptimizedModelPath(filename) {
     throw new Error(`Invalid model filename: ${filename}`);
   }
 
-  const sourcePath = path.join(SOURCE_DIR, filename);
+  const sourceDir = getSourceDir();
+  const sourcePath = path.join(sourceDir, filename);
   const cacheFilename = filename.replace(/\.glb$/, '_opt.glb');
   const cachePath = path.join(CACHE_DIR, cacheFilename);
 
   if (!fs.existsSync(sourcePath)) {
-    throw new Error(`Source model not found: ${filename}`);
+    throw new Error(`Source model not found: ${filename} (looked in ${sourceDir})`);
   }
 
   ensureCacheDir();