WP-02: encrypted settings, SMTP mail, job runner and cron scheduler

AES-256-GCM secret storage keyed by MASTER_KEY, SMTP settings with test mail
(lettre), persisted job runs with log and status, JobRunner with per-kind
concurrency guard, 6-field cron schedules with defaults, scheduler loop.
Settings and Jobs pages in the UI. FAKE_HOST mode for dev machines.

Tests: 30 application, 8 infrastructure, 23 API, 16 Vitest, 6 Playwright.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/playwright.config.ts

@@ -19,6 +19,8 @@ export default defineConfig({
       env: {
         DATABASE_URL: 'sqlite::memory:',
         JWT_SECRET: 'e2e-test-secret-do-not-use-in-production',
+        MASTER_KEY: '000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f',
+        FAKE_HOST: 'true',
         BOOTSTRAP_ADMIN_EMAIL: 'admin@example.com',
         BOOTSTRAP_ADMIN_PASSWORD: 'admin-password-123',
         BIND: '127.0.0.1:8080',