feat(api): scaffold Fastify server with health route

- ESM Fastify 4 with Pino logger (pretty-print in dev only)
- Plugins: helmet, cors (allowlist via CORS_ORIGINS), rate-limit, sensible
- Zod-validated environment config in src/config/env.ts
- Modular structure under src/modules with /health route
- tsx watch for dev, tsc for build, dist/server.js as production entry

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/.eslintrc.cjs

@@ -0,0 +1,5 @@
+/** @type {import('eslint').Linter.Config} */
+module.exports = {
+  root: true,
+  extends: ['@ketopath/eslint-config/node.cjs'],
+};