feat(server): add Prisma schema with all 8 data models

- User, CardType, Membership, WeekTemplate, TimeSlot, Booking, Order, StudioConfig
- PrismaService and global PrismaModule
- snake_case column mapping with camelCase TypeScript fields
- Proper indexes and unique constraints

packages/server/src/app.module.ts

@@ -1,6 +1,7 @@
 import { Module } from '@nestjs/common'
 import { ConfigModule } from '@nestjs/config'
 import { AppController } from './app.controller'
+import { PrismaModule } from './prisma/prisma.module'
 
 @Module({
   imports: [
@@ -8,6 +9,7 @@ import { AppController } from './app.controller'
       isGlobal: true,
       envFilePath: ['.env.local', '.env'],
     }),
+    PrismaModule,
   ],
   controllers: [AppController],
 })