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

.gitignore

@@ -33,3 +33,22 @@ PRIVATE_NOTES.md
 *.tmp
 *.bak
 *~
+
+# Node
+node_modules/
+.env
+*.log
+
+# Build artifacts
+dist/
+.next/
+coverage/
+
+# Test artifacts
+test-results/
+playwright-report/
+
+# Data
+data/
+*.sqlite
+*.db