feat: add real Stripe integration, e2e tests, and Pi deployment

Replace documentation-only repo with working code:

- Stripe integration: webhook handler (8 event types), billing API
  (customers, checkout, payments, subscriptions, invoices)
- Express API server with health endpoint, structured logging
- E2E tests (Playwright): health, webhook signature verification,
  billing API validation
- Unit tests: webhook event handler coverage for all event types
- Pi deployment: deploy.sh (rsync + systemd), NGINX load balancer
  across Pi cluster, Docker support
- CI/CD: test workflow, Pi deploy workflow, updated auto-deploy
  and self-healing to run real tests before deploying
- Move resume docs to docs/ to separate code from documentation

https://claude.ai/code/session_01Mf5Pg82fV6BTRS9GnpV7nr

.env.example

@@ -0,0 +1,24 @@
+# Stripe
+STRIPE_SECRET_KEY=sk_test_your_key_here
+STRIPE_PUBLISHABLE_KEY=pk_test_your_key_here
+STRIPE_WEBHOOK_SECRET=whsec_your_webhook_secret_here
+
+# Server
+PORT=3000
+NODE_ENV=production
+LOG_LEVEL=info
+
+# Pi Deployment
+PI_HOST_1=192.168.1.100
+PI_HOST_2=192.168.1.101
+PI_HOST_3=192.168.1.102
+PI_USER=pi
+PI_DEPLOY_PATH=/opt/blackroad
+PI_SSH_KEY=~/.ssh/id_ed25519
+
+# Health Check
+DEPLOY_URL=http://localhost:3000
+HEALTH_CHECK_INTERVAL=30000
+
+# Database (optional - for persistent billing state)
+DATABASE_URL=sqlite:./data/blackroad.db