test(e2e): disable rate limiting in the Playwright backend webserver

RATE_LIMIT_ENABLED now defaults on regardless of DEBUG; the e2e suite
logs in dozens of times per run from one IP and trips the per-minute
auth limits (429 at helpers/api.ts login).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/playwright.config.ts

@@ -31,6 +31,9 @@ export default defineConfig({
       env: {
         ...process.env,
         DEBUG: process.env.PLAYWRIGHT_DEBUG || 'true',
+        // e2e logs in dozens of times per run from one IP — the per-minute
+        // auth limits would 429 every spec after the first few.
+        RATE_LIMIT_ENABLED: 'false',
         SECRET_KEY: process.env.PLAYWRIGHT_SECRET_KEY || 'playwright-test-secret-key',
         DATABASE_URL: backendDatabaseUrl,
         DATABASE_URL_SYNC: backendDatabaseUrlSync,