fix: copy prisma.config.ts to runner stage and auto-run migrations on startup

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

prisma.config.ts

@@ -1,8 +1,10 @@
-// This file was generated by Prisma, and assumes you have installed the following:
-// npm install --save-dev prisma dotenv
-import "dotenv/config";
 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: {