fix: simplify prisma.config.ts and exclude it from Next.js tsconfig

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prisma.config.ts

@@ -1,10 +1,5 @@
 import { defineConfig } from "prisma/config";
 
-// dotenv only needed for local dev (docker-compose passes env vars directly)
-if (process.env.NODE_ENV !== "production") {
-  await import("dotenv/config").catch(() => {});
-}
-
 export default defineConfig({
   schema: "prisma/schema.prisma",
   migrations: {