Accept DB_DATABASE (Coolify convention) in addition to DB_NAME

Coolify auto-injected env vars from an attached Postgres use DB_DATABASE,
but the cotizador code read DB_NAME. Now both are accepted (DB_DATABASE
takes priority) across db.ts, seed.ts, and prisma.config.ts so attaching a
managed Postgres in Coolify Just Works.

src/lib/db.ts

@@ -11,7 +11,7 @@ function createPrismaClient() {
     port: parseInt(process.env.DB_PORT || "5432"),
     user: process.env.DB_USER || "postgres",
     password: process.env.DB_PASSWORD || "postgres",
-    database: process.env.DB_NAME || "cotizador_e3",
+    database: process.env.DB_DATABASE || process.env.DB_NAME || "cotizador_e3",
   });
   return new PrismaClient({ adapter });
 }