ci: Add check for empty German translations in lint task

- Check that all German msgstr entries are filled (excluding header)
- Use awk to filter out header msgstr "" entries
- Fail lint if any empty translations are found

Justfile

@@ -32,6 +32,8 @@ lint:
     mix format --check-formatted
     mix compile --warnings-as-errors
     mix credo
+    # Check that all German translations are filled (UI must be in German)
+    @bash -c 'for file in priv/gettext/de/LC_MESSAGES/*.po; do awk "/^msgid \"\"$/{header=1; next} /^msgid /{header=0} /^msgstr \"\"$/ && !header{print FILENAME\":\"NR\": \" \$0; exit 1}" "$file" || exit 1; done'
     mix gettext.extract --check-up-to-date
 
 audit: