ci: add .pot freshness and .mo compilation checks

[Krupakar-Reddy-S]

Description

Problem or Issue being addressed

Two localization CI gaps called out as explicit TODOs in l10n/README.md:

1. Line 272: "Github Action to auto-generate messages.pot and fail a PR update if out of date" — a contributor can add or change translatable strings (_(), _mft(), ButtonOption()) and forget to regenerate messages.pot. Translators on Transifex never see the new strings until someone notices manually.

2. Line 304: *"Github Actions automation to regenerate/verify that *.mo files have been updated after .po changes" — currently there is no CI check that catches stale or broken .mo files in the translations submodule.

Solution

Adds two new CI jobs to tests.yml:

pot-freshness — Copies the existing messages.pot, re-runs python setup.py extract_messages, strips the POT-Creation-Date timestamp from both files (Babel always writes the current time, which would cause a false diff), and diffs the two. Fails with a clear ::error:: message if the content changed.

mo-compilation — Runs python setup.py compile_catalog to recompile all .mo files from their .po sources, then diffs inside the translations submodule. Emits a ::warning:: annotation if any .mo file changed. Currently warns but does not fail, since ca and nl have stale .mo files at the pinned submodule commit. A TODO comment marks where to flip to exit 1 once the submodule is fixed.

Both jobs run independently of the test matrix and only need Babel, so they are lightweight and fast.

Also creates CONTRIBUTING.md with a localization section explaining when and how to run extract_messages locally. No existing contributing guide was found in the repo.

Note: the translations submodule is moving toward not committing .mo files at all (commit 76c6f57 removed them, .gitignore excludes *.mo). Once the main repo bumps its submodule pointer past that commit, the mo-compilation check becomes a "does compile_catalog succeed" validation — still useful for catching malformed .po files.

Additional Information

Verified locally three ways:

• python setup.py extract_messages + timestamp-stripped diff: no false positives
• Docker (docker compose run): both checks pass/warn as expected
• act: jobs succeed end-to-end

Screenshots

N/A — CI workflow changes, no UI modifications.

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This pull request is categorized as a:

• New feature
• Bug fix
• Code refactor
• Documentation
• Other

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Checklist

I ran pytest locally

• All tests passed before submitting the PR
• I couldn't run the tests
• N/A

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I included screenshots of any new or modified screens

Should be part of the PR description above.

• Yes
• No
• N/A

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I added or updated tests

Any new or altered functionality should be covered in a unit test. Any new or updated sequences require FlowTests.

• Yes
• No, I'm a fool
• N/A

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I tested this PR hands-on on the following platform(s):

• Raspberry Pi OS Manual Build
• SeedSigner OS on a Pi0/Pi0W board
• Emulator

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I have reviewed these notes:

• Keep your changes limited in scope.
• If you uncover other issues or improvements along the way, ideally submit those as a separate PR.
• The more complicated the PR, the harder it is to review, test, and merge.
• We appreciate your efforts, but we're a small team of volunteers so PR review can be a very slow process.
• Please only "@" mention a contributor if their input is truly needed to enable further progress.

• I understand

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[wolgwang1729]

LGTM. I pulled this branch locally and validated the pot-freshness behavior by changing a translatable UI string without regenerating messages.pot. The check correctly ignored POT-Creation-Date noise, detected the real diff, and failed with a clear, actionable error. Great CI improvement.

Minor cross-platform note (non-blocking): the current sed -i line is fine for Ubuntu CI, but macOS/BSD sed requires an explicit backup suffix (for example, sed -i '' ). If contributors copy-paste the command locally on macOS, it may fail unless adjusted.