test: add Playwright E2E infrastructure with smoke test

Set up Playwright with Chromium, dev server auto-start, test helpers
for seeding bots and programmatic auth. Added smoke spec that verifies
homepage and leaderboard load without crashes.

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

e2e/helpers/setup.ts

@@ -0,0 +1,46 @@
+/**
+ * E2E test setup helpers.
+ * Provides utilities for seeding test data and managing test state.
+ */
+
+/** Wait for the dev server to be ready */
+export async function waitForServer(baseURL: string, timeoutMs = 10_000): Promise<void> {
+  const start = Date.now()
+  while (Date.now() - start < timeoutMs) {
+    try {
+      const res = await fetch(baseURL)
+      if (res.ok) return
+    } catch {
+      // Server not ready yet
+    }
+    await new Promise(r => setTimeout(r, 500))
+  }
+  throw new Error(`Server at ${baseURL} did not start within ${timeoutMs}ms`)
+}
+
+/** Seed a mock bot via the API for testing */
+export async function seedBot(baseURL: string, name: string, pubkey: string): Promise<{ id: string; secret: string }> {
+  const res = await fetch(`${baseURL}/api/auth/register`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({
+      pubkey,
+      name,
+      webhookUrl: 'http://mock.local',
+    }),
+  })
+
+  if (!res.ok) {
+    const body = await res.text()
+    throw new Error(`Failed to seed bot ${name}: ${res.status} ${body}`)
+  }
+
+  return res.json()
+}
+
+/** Generate a random hex pubkey for testing */
+export function randomPubkey(): string {
+  const bytes = new Uint8Array(32)
+  crypto.getRandomValues(bytes)
+  return Array.from(bytes).map(b => b.toString(16).padStart(2, '0')).join('')
+}