feat: Reinitialize frontend with SvelteKit and TypeScript

- Delete old Vite+Svelte frontend
- Initialize new SvelteKit project with TypeScript
- Configure Tailwind CSS v4 + DaisyUI
- Implement JWT authentication with auto-refresh
- Create login page with form validation (Zod)
- Add protected route guards
- Update Docker configuration for single-stage build
- Add E2E tests with Playwright (6/11 passing)
- Fix Svelte 5 reactivity with $state() runes

Known issues:
- 5 E2E tests failing (timing/async issues)
- Token refresh implementation needs debugging
- Validation error display timing

frontend/node_modules/happy-dom/lib/event/DataTransferItemList.js

@@ -0,0 +1,40 @@
+import File from '../file/File.js';
+import DataTransferItem from './DataTransferItem.js';
+/**
+ *
+ */
+export default class DataTransferItemList extends Array {
+    /**
+     * Adds an item.
+     *
+     * @param item Item.
+     * @param type Type.
+     */
+    add(item, type) {
+        if (item instanceof File) {
+            this.push(new DataTransferItem(item));
+            return;
+        }
+        if (!type) {
+            throw new TypeError(`Failed to execute 'add' on 'DataTransferItemList': parameter 1 is not of type 'File'.`);
+        }
+        this.push(new DataTransferItem(item, type));
+    }
+    /**
+     * Removes an item.
+     *
+     * @param index Index.
+     */
+    remove(index) {
+        this.splice(index, 1);
+    }
+    /**
+     * Clears list.
+     */
+    clear() {
+        while (this.length) {
+            this.pop();
+        }
+    }
+}
+//# sourceMappingURL=DataTransferItemList.js.map