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

package.json

@@ -0,0 +1,24 @@
+{
+  "name": "gruperly",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "workspaces": [
+    "apps/*",
+    "packages/*"
+  ],
+  "scripts": {
+    "dev": "turbo dev",
+    "build": "turbo build",
+    "lint": "turbo lint",
+    "typecheck": "turbo typecheck",
+    "db:generate": "bun run --filter @gruperly/api db:generate",
+    "db:migrate": "bun run --filter @gruperly/api db:migrate",
+    "db:push": "bun run --filter @gruperly/api db:push",
+    "db:studio": "bun run --filter @gruperly/api db:studio"
+  },
+  "devDependencies": {
+    "turbo": "^2.3.3"
+  },
+  "packageManager": "bun@1.4.0"
+}