Add CI job to build production artifact and run smoke tests

[robertocarlous]

Body:

Add a CI workflow that runs npm ci --production, npm run build, and a minimal smoke-check that starts the built server and verifies /health. This prevents shipping artifacts that fail to start.

Acceptance Criteria:

• CI workflow builds the production artifact and runs a smoke-check.
• Smoke-check verifies /health endpoint and exits non-zero on failure.
• CI fails when build or smoke-check fails.

[Yormee-103]

Hello maintainer i would like to work on this issue, i understand the scope of the project

[grantfox-oss]

🦊 GrantFox — @Yormee-103 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #152)
2. Your PR will be reviewed by the Neurowealth maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@Yormee-103's PR #156 was approved and merged by @robertocarlous.

🏆 @Yormee-103: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (118 total points). Track your full progress on GrantFox.

👏 Great work, @Yormee-103! Keep contributing to Neurowealth.