test(e2e): Playwright UI smoke + Go integration tests against MAS

- Playwright e2e against Vite dev server (LoginScreen renders, homeserver
  visible, version pinned). Fallback documented to swap to `wails dev
  -browser` via WAILS_DEV_URL when full backend bindings are required.
- Go integration tests (//go:build integration,goolm) for Start +
  ListRooms + LoadTimeline + SendText + GetDiagnostics against real
  Synapse. Skip cleanly if MATRIX_INTEGRATION_TOKEN/USER env vars unset
  so CI never breaks unattended.
- pnpm e2e/e2e:ui/e2e:report scripts. Per-run keyring namespace +
  t.TempDir XDG_CONFIG_HOME so integration tests don't clobber the
  production keyring entry.

E2E.md explains how to run each layer + limits (OIDC not automated).

frontend/playwright.config.ts

@@ -0,0 +1,35 @@
+import { defineConfig } from "@playwright/test";
+
+// E2E config — runs Vite dev server (not full `wails dev`) on a fixed port so
+// Playwright can hit the React UI without needing the Go backend compiled with
+// goolm. LoginScreen + initial App boot render fine because the only Wails
+// runtime call (GetLastUserID) throws inside a try/finally that flips the
+// loading overlay off. See E2E.md for the rationale + how to swap to `wails
+// dev -browser` if/when the full backend is available.
+
+const DEV_PORT = Number(process.env.WAILS_E2E_PORT || 5180);
+const BASE_URL = process.env.WAILS_DEV_URL || `http://localhost:${DEV_PORT}`;
+
+export default defineConfig({
+  testDir: "./e2e",
+  timeout: 30_000,
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 2 : 0,
+  workers: 1,
+  reporter: process.env.CI ? "github" : "list",
+  use: {
+    baseURL: BASE_URL,
+    headless: true,
+    trace: "on-first-retry",
+    screenshot: "only-on-failure",
+  },
+  webServer: {
+    command: `pnpm dev --port ${DEV_PORT} --strictPort`,
+    url: BASE_URL,
+    timeout: 60_000,
+    reuseExistingServer: !process.env.CI,
+    stdout: "pipe",
+    stderr: "pipe",
+  },
+});