feat(cli): rspack preview support for nodeEnv flag and default env

[chenjiahan]

Summary

Enhance the rspack preview command:

• Add support for --nodeEnv flag
• Set process.env.NODE_ENV to production by default (align with Rsbuild and other community tools)

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[netlify]

✅ Deploy Preview for rspack ready!

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[codspeed-hq]

CodSpeed Performance Report

Merging #9543 will not alter performance

_{Comparing preview_env_0304 (ab81644) with main (44f96be)}

Summary

✅ 7 untouched benchmarks