feat: initialize monorepo structure with Bun and Turborepo

- Add package.json for the root with workspace configuration and scripts
- Create @gruperly/config package with TypeScript configuration
- Establish shared package @gruperly/shared with Zod schemas for validation
- Implement group, student, and payment schemas using Zod
- Set up TypeScript configuration for shared package
- Document stack architecture and technical specifications in stack.md
- Configure Turborepo with build, dev, lint, and typecheck tasks

apps/api/src/routes/groups.ts

@@ -0,0 +1,5 @@
+import { Hono } from 'hono'
+
+export const groupsRoutes = new Hono()
+
+groupsRoutes.get('/', (c) => c.json([]))