Replace dev feature flag with LOCAL_DEV

[Sanket17052006]

Part of #12946

This PR replaces the legacy "dev" in ctx.features / "dev" in config.features checks with get_ol_env().LOCAL_DEV, as it's an environment indicator (only enabled locally,not in testing/production).

Technical

• Removed dev: enabled from conf/openlibrary.yml
• Replaced all "dev" in ... features checks with get_ol_env().LOCAL_DEV.
• Added get_ol_env to web.template.Template.globals for template access
• Removed stale # dev: bool comment from the pydantic Features model.
• Unused import infogami removed from admin.py and deprecated_handler.py

Testing

No behavioral change: LOCAL_DEV is never set in production, same as old dev flag

Screenshot

N/A

Stakeholders

@RayBB

[openlibrary-bot]

Thanks for the PR, @Sanket17052006!

A reviewer must first be assigned. There are currently 13 open PRs of equal or higher priority ahead of yours.

PR triage checklist (maintainers / Richy)

• PR description — not empty; explains what the change does and how to verify it
• References an issue — PR body contains a #NNN reference
  • Linked issue is triaged — has a Priority: * label (not just Needs: Triage)
  • Linked issue is assigned — has at least one assignee
• Commit history clean — no WIP/fixup/conflict noise; commit messages are meaningful
• CI passing — no failing check-runs
• Test cases present — if the change touches substantive logic, test coverage exists or is explained
• Proof of testing — PR body includes a description of what was tested, a screenshot, or a video

Note

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— Richy, via PAM (Open Library's Project AI Manager)

[mekarpeles]

This needs to be evaluated by staff and also tested on testing + prod server.