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/package.json

@@ -0,0 +1,28 @@
+{
+  "name": "@gruperly/api",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "bun --watch src/index.ts",
+    "start": "bun src/index.ts",
+    "build": "bun build ./src/index.ts --target bun --outdir dist",
+    "typecheck": "tsc --noEmit",
+    "db:generate": "prisma generate",
+    "db:migrate": "prisma migrate dev",
+    "db:push": "prisma db push",
+    "db:studio": "prisma studio"
+  },
+  "dependencies": {
+    "@gruperly/shared": "workspace:*",
+    "@hono/zod-validator": "^0.8.0",
+    "better-auth": "^1.1.0",
+    "hono": "^4.6.0"
+  },
+  "devDependencies": {
+    "@types/bun": "^1.0.0",
+    "prisma": "^6.0.0",
+    "@prisma/client": "^6.0.0",
+    "typescript": "^5.7.0"
+  }
+}