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/app.module.ts

@@ -0,0 +1,15 @@
+import { Module } from '@nestjs/common';
+import { ConfigModule } from '@nestjs/config';
+import { PrismaModule } from './prisma/prisma.module';
+import { AuthModule } from './auth/auth.module';
+import { KcModule } from './kc/kc.module';
+
+@Module({
+  imports: [
+    ConfigModule.forRoot({ isGlobal: true }),
+    PrismaModule,
+    AuthModule,
+    KcModule,
+  ],
+})
+export class AppModule {}