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

.gitignore

@@ -136,3 +136,18 @@ dist
 .yarn/install-state.gz
 .pnp.*
 
+# Bun
+.bun
+bun.lockb
+
+# Turborepo
+.turbo
+
+# Prisma
+apps/api/prisma/dev.db
+apps/api/prisma/migrations/dev/
+*.db
+
+# env
+apps/api/.env
+