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/lib/runner/sigIntWatcher.js

@@ -0,0 +1,96 @@
+"use strict";
+var __defProp = Object.defineProperty;
+var __getOwnPropDesc = Object.getOwnPropertyDescriptor;
+var __getOwnPropNames = Object.getOwnPropertyNames;
+var __hasOwnProp = Object.prototype.hasOwnProperty;
+var __export = (target, all) => {
+  for (var name in all)
+    __defProp(target, name, { get: all[name], enumerable: true });
+};
+var __copyProps = (to, from, except, desc) => {
+  if (from && typeof from === "object" || typeof from === "function") {
+    for (let key of __getOwnPropNames(from))
+      if (!__hasOwnProp.call(to, key) && key !== except)
+        __defProp(to, key, { get: () => from[key], enumerable: !(desc = __getOwnPropDesc(from, key)) || desc.enumerable });
+  }
+  return to;
+};
+var __toCommonJS = (mod) => __copyProps(__defProp({}, "__esModule", { value: true }), mod);
+var sigIntWatcher_exports = {};
+__export(sigIntWatcher_exports, {
+  SigIntWatcher: () => SigIntWatcher
+});
+module.exports = __toCommonJS(sigIntWatcher_exports);
+class SigIntWatcher {
+  constructor() {
+    this._hadSignal = false;
+    let sigintCallback;
+    this._sigintPromise = new Promise((f) => sigintCallback = f);
+    this._sigintHandler = () => {
+      FixedNodeSIGINTHandler.off(this._sigintHandler);
+      this._hadSignal = true;
+      sigintCallback();
+    };
+    FixedNodeSIGINTHandler.on(this._sigintHandler);
+  }
+  promise() {
+    return this._sigintPromise;
+  }
+  hadSignal() {
+    return this._hadSignal;
+  }
+  disarm() {
+    FixedNodeSIGINTHandler.off(this._sigintHandler);
+  }
+}
+class FixedNodeSIGINTHandler {
+  static {
+    this._handlers = [];
+  }
+  static {
+    this._ignoreNextSIGINTs = false;
+  }
+  static {
+    this._handlerInstalled = false;
+  }
+  static {
+    this._dispatch = () => {
+      if (this._ignoreNextSIGINTs)
+        return;
+      this._ignoreNextSIGINTs = true;
+      setTimeout(() => {
+        this._ignoreNextSIGINTs = false;
+        if (!this._handlers.length)
+          this._uninstall();
+      }, 1e3);
+      for (const handler of this._handlers)
+        handler();
+    };
+  }
+  static _install() {
+    if (!this._handlerInstalled) {
+      this._handlerInstalled = true;
+      process.on("SIGINT", this._dispatch);
+    }
+  }
+  static _uninstall() {
+    if (this._handlerInstalled) {
+      this._handlerInstalled = false;
+      process.off("SIGINT", this._dispatch);
+    }
+  }
+  static on(handler) {
+    this._handlers.push(handler);
+    if (this._handlers.length === 1)
+      this._install();
+  }
+  static off(handler) {
+    this._handlers = this._handlers.filter((h) => h !== handler);
+    if (!this._ignoreNextSIGINTs && !this._handlers.length)
+      this._uninstall();
+  }
+}
+// Annotate the CommonJS export names for ESM import in node:
+0 && (module.exports = {
+  SigIntWatcher
+});