Add dev/prod environment support for cloud API to main

[stahir715]

Summary

Licensing layer

• Apache-2.0 extension (3D Slicer, wellness/veterinary module, partner SDK, language binding)
• AGPL-3.0 core (firmware, sensing/beamforming/reconstruction/signal-processing/calibration algorithms, hardware reference design)
• Docs / data / tooling only
• This PR moves a file between the AGPL core and the Apache layer — if checked, this is NOT an ordinary PR: it requires the license-manifest change process (and board approval for anything leaving the core). Link the approval.

Checklist

• Commits are signed off (DCO): git commit -s
• New files carry the correct SPDX-License-Identifier for their layer
• Tests and docs updated
• No incompatible third-party code introduced
• CI is green and CODEOWNERS review requested

Notes for reviewers

Restores dev/prod environment selection for the cloud sync Cloud class. This was originally added on the add-cloud-dev-prod-environment-support branch (commit 04fd1f8) but never merged into main. That branch is now ~70 commits stale, so this PR cherry-picks that commit onto current main rather than merging the branch directly. Cloud.init gains an optional environment parameter (defaults to "prod", unchanged from current behavior) that selects between API_URL_PROD and the newly added API_URL_DEV.

[ebrahimebrahim]

I added validation so only "dev" and "prod" are accepted. Previously, a typo such as "deev" silently selected production, which could send development sync traffic to the production service.