Clean repo updates and harden setup docs

[ZEN-PUNK]

Summary

• clean and consolidate repository updates on branch berlin-hack
• harden setup documentation in README.md to avoid exposing keys/endpoints
• add template-driven env setup (server/.env.example) and related server workflow updates

Notes

• this PR includes broad cleanup/deletion of legacy docs and test artifacts
• no real keys/endpoints are included in committed docs

Validation

• branch pushed successfully
• commit: 9521a4c

[gitguardian]

️✅ There are no secrets present in this pull request anymore.

If these secrets were true positive and are still valid, we highly recommend you to revoke them.
While these secrets were previously flagged, we no longer have a reference to the
specific commits where they were detected. Once a secret has been leaked into a git
repository, you should consider it compromised, even if it was deleted immediately.
Find here more information about risks.

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