feat: initialize backend with NestJS, PostgreSQL, and Prisma

- Add package.json for backend dependencies and scripts.
- Create Prisma schema for multi-tenant event management.
- Implement main application module and configure global settings.
- Develop authentication module with JWT and Authentik integration.
- Create DTOs for guest account creation and KC management.
- Implement role-based access control with custom guards and decorators.
- Add services and controllers for managing KCs and guest accounts.
- Set up global validation and CORS in the main application entry point.
- Establish Prisma module for database access throughout the application.
- Document project plan and architecture for multi-tenant platform.

src/prisma/prisma.module.ts

@@ -0,0 +1,17 @@
+import { Global, Module } from '@nestjs/common';
+import { PrismaClient } from '@prisma/client';
+
+/// Shared Prisma connection; injected wherever DB access is needed.
+@Global()
+@Module({
+  providers: [
+    {
+      provide: PrismaClient,
+      useFactory: () => new PrismaClient(),
+    },
+  ],
+  exports: [PrismaClient],
+})
+export class PrismaModule {}
+
+export { PrismaClient };