Switch from standalone to standard Next.js build

Removes output: "standalone" from next.config.js, updates build/start/preview
scripts to use next build/next start, and updates Dockerfile to copy .next
output directory and run via bun run start instead of server.js.

https://claude.ai/code/session_014126WHVRT8mftmqkU6dajG

Dockerfile

@@ -23,8 +23,7 @@ ENV NODE_ENV=production \
     PORT=3000 \
     HOSTNAME=0.0.0.0
 
-COPY --from=build /usr/src/app/.next/standalone ./
-COPY --from=build /usr/src/app/.next/static ./.next/static
+COPY --from=build /usr/src/app/.next ./.next
 COPY --from=build /usr/src/app/public ./public
 COPY --from=install /usr/src/app/node_modules node_modules
 COPY --from=build /usr/src/app/package.json ./package.json
@@ -36,4 +35,4 @@ RUN chmod -R a+rX drizzle public migrate.ts
 
 USER bun
 EXPOSE 3000
-CMD ["sh", "-c", "bun migrate.ts && bun server.js"]
+CMD ["sh", "-c", "bun migrate.ts && bun run start"]