fix: preserve process.env reference using Object.assign

[rafaumeu]

Summary

Fixes #46

vite.config.js was overwriting the entire process.env object with a direct assignment, which replaces the original reference and can break imported modules that captured the reference earlier.

Fix

Replaced process.env = { ...process.env, ...loadEnv(...) } with Object.assign(process.env, loadEnv(...)) which mutates in-place.

Testing

• No behavior change in normal usage
• Preserves all existing env vars and references