fix: Prisma 7 adapter-based connection (no url in schema)

- Use @prisma/adapter-pg for PrismaClient (Prisma 7 removed datasourceUrl/datasources)
- prisma.config.ts: migrate.url for CLI commands
- schema.prisma: no url in datasource (Prisma 7 requirement)

prisma/schema.prisma

@@ -9,7 +9,6 @@ generator client {
 
 datasource db {
   provider = "postgresql"
-  url      = env("DATABASE_URL")
 }
 
 // ======================== ENUMS =============================