Bump next and @react-email/preview-server

Bumps [next](https://github.com/vercel/next.js) to 15.5.7 and updates ancestor dependency [@react-email/preview-server](https://github.com/resend/react-email/tree/HEAD/packages/preview-server). These dependencies need to be updated together.


Updates `next` from 15.5.2 to 15.5.7
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](https://github.com/vercel/next.js/compare/v15.5.2...v15.5.7)

Updates `@react-email/preview-server` from 4.3.2 to 5.0.6
- [Release notes](https://github.com/resend/react-email/releases)
- [Changelog](https://github.com/resend/react-email/blob/canary/packages/preview-server/CHANGELOG.md)
- [Commits](https://github.com/resend/react-email/commits/@react-email/preview-server@5.0.6/packages/preview-server)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.7
  dependency-type: indirect
- dependency-name: "@react-email/preview-server"
  dependency-version: 5.0.6
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -141,7 +141,7 @@
     "devDependencies": {
         "@dotenvx/dotenvx": "1.51.1",
         "@esbuild-plugins/tsconfig-paths": "0.1.2",
-        "@react-email/preview-server": "4.3.2",
+        "@react-email/preview-server": "5.0.6",
         "@tailwindcss/postcss": "^4.1.17",
         "@tanstack/react-query-devtools": "^5.90.2",
         "@types/better-sqlite3": "7.6.12",