refactor: migrate backend to pnpm monorepo with Hono module architecture

- Replace Bun with pnpm 9 + Turborepo + tsx; apps/api renamed to apps/backend
- Split backend into http/, modules/, lib/ layers mirroring tai-specguard
- Add use-case + Result pattern, Problem Details RFC 7807, basePath /api/v1
- Mount Better Auth at /api/v1/auth, keep session-auth whitelist
- Split Prisma schema into prisma/models/*, generate into generated/
- Rework packages/shared into lib/ + schemas/ with pagination DTOs
- Implement health, groups, students, payments, waitlist modules
- Add vitest suite with prisma mocks (21 tests), biome lint
- Point web client to /api/v1/auth and /api/v1/groups/from-organization

apps/backend/src/modules/groups/routes.ts

@@ -0,0 +1,10 @@
+import { Hono } from 'hono';
+import createFromOrganizationRoute from './features/create-from-organization/route';
+import getAllRoute from './features/get-all/route';
+
+const routes = new Hono();
+
+routes.route('/', getAllRoute);
+routes.route('/from-organization', createFromOrganizationRoute);
+
+export default routes;