feat: verify Turborepo pipeline — all 8 packages build and test

Adds packageManager field to root package.json (required by turbo v2.9),
loads .env via dotenv in API jest config so Prisma integration tests find
DATABASE_URL when run from the monorepo root. pnpm build + pnpm test: 8/8 passing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/jest.config.js

@@ -1,3 +1,6 @@
+const path = require('path');
+require('dotenv').config({ path: path.resolve(__dirname, '../../.env') });
+
 module.exports = {
   moduleFileExtensions: ['js', 'json', 'ts'],
   rootDir: 'src',