chore: migrate to pnpm workspaces monorepo with Turborepo

- Restructure directories: apps/api, apps/admin, apps/website
- Add root pnpm-workspace.yaml, turbo.json, .prettierrc, .gitignore
- Rename packages to @inkreach/api, @inkreach/admin, @inkreach/website
- Add shared packages: packages/tsconfig, packages/shared-types
- Add pnpm.onlyBuiltDependencies for native builds
- Update docs: README.md, structs.md
- All three projects build successfully

apps/api/src/prisma/prisma.service.ts

@@ -0,0 +1,20 @@
+import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
+import { PrismaClient } from '@prisma/client';
+
+/**
+ * Global Prisma client wrapper.
+ *
+ * - `onModuleInit`: connects to the database so the first request
+ *   does not pay the connection cost.
+ * - `onModuleDestroy`: cleanly disconnects during shutdown.
+ */
+@Injectable()
+export class PrismaService extends PrismaClient implements OnModuleInit, OnModuleDestroy {
+  async onModuleInit(): Promise<void> {
+    await this.$connect();
+  }
+
+  async onModuleDestroy(): Promise<void> {
+    await this.$disconnect();
+  }
+}