Implement comprehensive frontend integration testing with Playwright

- Add Playwright E2E testing framework with cross-browser support (Chrome, Firefox)
- Create authentication helpers for CalDAV server integration
- Implement calendar interaction helpers with event creation, drag-and-drop, and view switching
- Add comprehensive drag-and-drop test suite with event cleanup
- Configure CI/CD integration with Gitea Actions for headless testing
- Support both local development and CI environments with proper dependency management
- Include video recording, screenshots, and HTML reporting for test debugging
- Handle Firefox-specific timing and interaction challenges with force clicks and timeouts

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/e2e/node_modules/playwright/jsx-runtime.js

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * 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.
+ */
+
+function jsx(type, props, key) {
+  return {
+    __pw_type: 'jsx',
+    type,
+    props,
+    key,
+  };
+}
+
+function jsxs(type, props, key) {
+  return {
+    __pw_type: 'jsx',
+    type,
+    props,
+    key,
+  };
+}
+
+// this is used in <></> notation
+const Fragment = { __pw_jsx_fragment: true };
+
+module.exports = {
+  Fragment,
+  jsx,
+  jsxs,
+};