test(dashboard): add Playwright e2e scaffolding with smoke spec

Milestone A of the frontend test plan. Sets up the test rig — config,
globalSetup that probes the backend and seeds an admin session into
storageState, lightweight fixtures, and a 3-test smoke spec — without
yet covering any user journeys (those land in Milestone B).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/tests/e2e/fixtures/ids.ts

@@ -0,0 +1,42 @@
+/* eslint-disable no-empty-pattern -- Playwright fixtures require an
+   object-pattern first arg; these fixtures don't depend on any other
+   fixture so the pattern is intentionally empty. */
+import { test as base } from '@playwright/test';
+import { randomBytes } from 'node:crypto';
+
+// Tests share a single backend/Postgres. To avoid collisions we tag
+// every resource the test creates with a short random suffix plus the
+// Playwright worker index. This way two workers running the same spec
+// in parallel never fight over the same slug or username.
+
+export function shortId(): string {
+	return randomBytes(3).toString('hex');
+}
+
+export function uniqueSlug(prefix: string, workerIndex: number): string {
+	const cleaned = prefix
+		.toLowerCase()
+		.replace(/[^a-z0-9]+/g, '-')
+		.replace(/^-|-$/g, '');
+	return `e2e-${cleaned}-w${workerIndex}-${shortId()}`;
+}
+
+export function uniqueUsername(prefix: string, workerIndex: number): string {
+	// Username regex is [a-z0-9._-]{2,32}. Mirror the slug format.
+	const cleaned = prefix.toLowerCase().replace(/[^a-z0-9]+/g, '');
+	return `e2e${cleaned}w${workerIndex}${shortId()}`.slice(0, 32);
+}
+
+export const test = base.extend<{
+	uniqueSlug: (prefix: string) => string;
+	uniqueUsername: (prefix: string) => string;
+}>({
+	uniqueSlug: async ({}, use, testInfo) => {
+		await use((prefix) => uniqueSlug(prefix, testInfo.workerIndex));
+	},
+	uniqueUsername: async ({}, use, testInfo) => {
+		await use((prefix) => uniqueUsername(prefix, testInfo.workerIndex));
+	}
+});
+
+export { expect } from '@playwright/test';