ci: add .pot freshness and .mo compilation checks

.github/workflows/tests.yml

@@ -14,6 +14,48 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  pot-freshness:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+      - name: Set up Python 3.10
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.10"
+      - name: Install Babel
+        run: pip install -r l10n/requirements-l10n.txt
+      - name: Verify messages.pot is up to date
+        run: |
+          cp l10n/messages.pot l10n/messages.pot.before
+          python setup.py extract_messages
+          # Strip POT-Creation-Date from both files before comparing — Babel
+          # always writes the current timestamp, which would cause a false diff.
+          sed -i '/^"POT-Creation-Date:/d' l10n/messages.pot.before l10n/messages.pot
+          diff l10n/messages.pot.before l10n/messages.pot || \
+            (echo "::error::l10n/messages.pot is out of date. Run 'python setup.py extract_messages' and commit the result." && exit 1)
+
+  mo-compilation:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+      - name: Set up Python 3.10
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.10"
+      - name: Install Babel
+        run: pip install -r l10n/requirements-l10n.txt
+      - name: Verify .mo files are up to date
+        run: |
+          python setup.py compile_catalog
+          # Warn but don't fail — ca and nl currently have stale .mo files.
+          # TODO: change to 'exit 1' once the translations submodule is fixed.
+          git -C src/seedsigner/resources/seedsigner-translations diff --exit-code || \
+            echo "::warning::Compiled .mo files are out of date. Run 'python setup.py compile_catalog' and commit the results to the seedsigner-translations submodule."
+
   test:
     runs-on: ubuntu-latest
     strategy:

CONTRIBUTING.md

@@ -0,0 +1,14 @@
+# Contributing to SeedSigner
+
+## Localization
+
+SeedSigner uses [Babel](https://babel.pocoo.org/) to extract translatable strings into `l10n/messages.pot`. If you add or change any string wrapped with `_()`, `_mft()`, or `ButtonOption()`, you must regenerate the `.pot` file before pushing:
+
+```bash
+pip install -r l10n/requirements-l10n.txt   # one-time setup
+python setup.py extract_messages
+```
+
+CI will fail if `l10n/messages.pot` is out of date.
+
+For more details on the three translation wrapping techniques and the full localization workflow, see `l10n/README.md`.