feat: auth fixtures y helpers de interaccion E2E

Implementa el issue 0022b — fixtures de Playwright para
autenticacion en Element Web y helpers de interaccion con rooms.

- element-auth.ts: flujo completo de login + cross-signing con
  recovery key, preparado para cachear sesion via storageState
- global-setup.ts: ejecuta login una vez antes de todos los tests,
  reutiliza sesion cacheada si tiene menos de 12 horas
- matrix-room.ts: helpers goToRoom, sendMessage, waitForBotReply,
  getLastMessage, assertNoDecryptionErrors (detecta "Unable to decrypt")
- login.spec.ts: 3 smoke tests validando sesion, E2EE y navegacion
- playwright.config.ts: configurado storageState para inyectar sesion

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

e2e/global-setup.ts

@@ -0,0 +1,70 @@
+import { chromium } from "@playwright/test";
+import * as path from "path";
+import * as fs from "fs";
+import * as dotenv from "dotenv";
+import { loginToElement } from "./fixtures/element-auth";
+
+dotenv.config({ path: path.resolve(__dirname, ".env") });
+
+const AUTH_DIR = path.resolve(__dirname, ".auth");
+const STATE_PATH = path.join(AUTH_DIR, "state.json");
+
+/**
+ * Global setup: ejecuta login una vez y guarda storageState
+ * para reutilizar en todos los tests sin repetir el login.
+ *
+ * Si state.json ya existe y no esta expirado, lo reutiliza.
+ */
+async function globalSetup() {
+  const elementURL = process.env.ELEMENT_URL || "http://localhost:8080";
+  const user = process.env.MATRIX_USER;
+  const password = process.env.MATRIX_PASSWORD;
+  const recoveryKey = process.env.MATRIX_RECOVERY_KEY;
+
+  if (!user || !password || !recoveryKey) {
+    throw new Error(
+      "Faltan variables de entorno: MATRIX_USER, MATRIX_PASSWORD, MATRIX_RECOVERY_KEY"
+    );
+  }
+
+  // Reutilizar sesion cacheada si existe y tiene menos de 12 horas
+  if (isStateFresh(STATE_PATH, 12 * 60 * 60 * 1000)) {
+    console.log("[global-setup] Reutilizando sesion cacheada");
+    return;
+  }
+
+  console.log("[global-setup] Ejecutando login en Element Web...");
+
+  // Asegurar que el directorio .auth existe
+  fs.mkdirSync(AUTH_DIR, { recursive: true });
+
+  const browser = await chromium.launch();
+  const context = await browser.newContext();
+  const page = await context.newPage();
+
+  try {
+    await loginToElement(page, {
+      url: elementURL,
+      user,
+      password,
+      recoveryKey,
+    });
+
+    await context.storageState({ path: STATE_PATH });
+    console.log("[global-setup] Sesion guardada en", STATE_PATH);
+  } finally {
+    await browser.close();
+  }
+}
+
+/** Verifica si el archivo de estado existe y tiene menos de maxAge ms. */
+function isStateFresh(filePath: string, maxAge: number): boolean {
+  try {
+    const stat = fs.statSync(filePath);
+    return Date.now() - stat.mtimeMs < maxAge;
+  } catch {
+    return false;
+  }
+}
+
+export default globalSetup;