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/waitlist/features/get-all/route.ts

@@ -0,0 +1,18 @@
+import type { WaitlistQuery } from '@gruperly/shared';
+import { WaitlistQuerySchema } from '@gruperly/shared';
+import { Hono } from 'hono';
+import { resultJson } from '@/http/problem-details';
+import { validate } from '@/http/validate';
+import { ListWaitlistEntries } from './use-case';
+
+const route = new Hono();
+
+route.get('/', validate.query(WaitlistQuerySchema), async (c) => {
+  const query = c.req.valid('query') as WaitlistQuery;
+  const useCase = new ListWaitlistEntries();
+  const result = await useCase.execute(query);
+
+  return resultJson(c, result);
+});
+
+export default route;

apps/backend/src/modules/waitlist/features/get-all/use-case.ts

@@ -0,0 +1,50 @@
+import type { PrismaClient } from '@generated/prisma/client';
+import type { ProblemDetails, Result, WaitlistEntryDto, WaitlistList, WaitlistQuery } from '@gruperly/shared';
+import { ok } from '@gruperly/shared';
+import { getPaginationMetadata, getPaginationOffset } from '@/lib/pagination';
+import prisma from '@/lib/prisma';
+
+type ListWaitlistEntriesDeps = {
+  db?: Pick<PrismaClient, 'waitlistEntry'>;
+};
+
+type WaitlistRecord = {
+  id: string;
+  email: string;
+  name: string | null;
+  status: WaitlistEntryDto['status'];
+  createdAt: Date;
+  updatedAt: Date;
+};
+
+function toWaitlistEntryDto(record: WaitlistRecord): WaitlistEntryDto {
+  return {
+    id: record.id,
+    email: record.email,
+    name: record.name,
+    status: record.status,
+    createdAt: record.createdAt.toISOString(),
+    updatedAt: record.updatedAt.toISOString(),
+  };
+}
+
+export class ListWaitlistEntries {
+  constructor(private readonly deps: ListWaitlistEntriesDeps = {}) {}
+
+  async execute(query: WaitlistQuery): Promise<Result<WaitlistList, ProblemDetails>> {
+    const db = this.deps.db ?? prisma;
+    const [records, total] = await Promise.all([
+      db.waitlistEntry.findMany({
+        skip: getPaginationOffset(query),
+        take: query.pageSize,
+        orderBy: { createdAt: 'desc' },
+      }),
+      db.waitlistEntry.count(),
+    ]);
+
+    return ok({
+      data: records.map(toWaitlistEntryDto),
+      pagination: getPaginationMetadata(query, total),
+    });
+  }
+}