Audit D2/D3/D4/D5: all four ApiTab buttons were handler-less and the
fields were hardcoded. Adds api/apiKeys.ts + api/webhooks.ts modules and
rewires ApiTab: loads the api-key prefix + webhook settings on mount;
Copy -> clipboard + snackbar; Regenerate -> confirm dialog -> POST
regenerate (full key shown once); Save Webhook -> PUT webhook-settings;
Test Webhook -> POST test with the result in a snackbar.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Дмитрий