Build: add vendored panel detection libraries

Add pre-built panel detection libraries to vendor directory.
These are copied from node_modules during the build process and
included with the application for panel detection functionality.

Included libraries:
- vendor/opencv/opencv.js - OpenCV.js for image processing
- vendor/tfjs/tf.min.js - TensorFlow.js for ML inference
- vendor/coco-ssd/coco-ssd.min.js - COCO-SSD model for object detection

These files enable the panel mode feature in the reader.

vendor/tfjs/tf.min.js

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright 2018 Google LLC. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * =============================================================================
+ */
+import '@tensorflow/tfjs-core';
+// tslint:disable-next-line: no-imports-from-dist
+import '@tensorflow/tfjs-core/dist/register_all_gradients';
+// tslint:disable-next-line: no-imports-from-dist
+import '@tensorflow/tfjs-core/dist/public/chained_ops/register_all_chained_ops';
+export * from '@tensorflow/tfjs-core';
+export * from '@tensorflow/tfjs-layers';
+export * from '@tensorflow/tfjs-converter';
+// Export data api as tf.data
+import * as data from '@tensorflow/tfjs-data';
+export { data };
+// Import and register backends.
+export * from '@tensorflow/tfjs-backend-cpu';
+export * from '@tensorflow/tfjs-backend-webgl';
+// Import versions of all sub-packages.
+import { version_core } from '@tensorflow/tfjs-core';
+import { version_cpu } from '@tensorflow/tfjs-backend-cpu';
+import { version_webgl } from '@tensorflow/tfjs-backend-webgl';
+import { version_data } from '@tensorflow/tfjs-data';
+import { version_layers } from '@tensorflow/tfjs-layers';
+import { version_converter } from '@tensorflow/tfjs-converter';
+import { version as version_union } from './version';
+export const version = {
+    'tfjs-core': version_core,
+    'tfjs-backend-cpu': version_cpu,
+    'tfjs-backend-webgl': version_webgl,
+    'tfjs-data': version_data,
+    'tfjs-layers': version_layers,
+    'tfjs-converter': version_converter,
+    'tfjs': version_union
+};
+//# sourceMappingURL=index.js.map