Add Playwright accessibility and mobile layout e2e tests

Set up end-to-end test infrastructure with Docker Compose test
environment, Playwright config, and automated global setup/teardown
that seeds a test database and creates fixtures via the API.

Tests cover 11 pages across both dark/light themes for WCAG 2.0 AA
accessibility (axe-core), and across 3 viewports (mobile, tablet,
desktop) for horizontal overflow and touch target validation.

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

frontend/e2e/global-teardown.ts

@@ -0,0 +1,21 @@
+import { execSync } from 'node:child_process'
+import { rmSync } from 'node:fs'
+import { resolve } from 'node:path'
+
+const COMPOSE_FILE = resolve(__dirname, '../../docker-compose.test.yml')
+const FIXTURES_PATH = resolve(__dirname, '.fixtures.json')
+
+export default async function globalTeardown() {
+  console.log('[teardown] Stopping test containers...')
+  execSync(`docker compose -f ${COMPOSE_FILE} down -v`, {
+    encoding: 'utf-8',
+    stdio: 'inherit',
+  })
+
+  try {
+    rmSync(FIXTURES_PATH)
+    console.log('[teardown] Removed fixtures file')
+  } catch {
+    // File may not exist if setup failed
+  }
+}