b93f5d5bdf
Adds test harness for the suite: - vitest.config.ts: happy-dom env, @/* alias, v8 coverage with 70% thresholds - setup.ts: env vars, global next/headers and next/navigation mocks - tsconfig.json: IDE alias resolution for test/ - __mocks__/prisma.ts: centralised Prisma mock auto-registered via vi.mock - fixtures/users.ts, fixtures/orders.ts: typed test data