Check translation contracts offline, add Swedish to the installer and enable the website languages

- Offline checks for terminal and website catalogs reject translations that change commands, paths, identifiers or placeholders
- Terminal and documentation texts that broke those contracts are corrected in every language
- Swedish can be chosen in the stable and beta installers
- The website routes, language switcher and exported pages cover the eight languages, with the shared website texts in each of them
- Website documentation translations are generated only when requested
- From PR #475 by @jcastro

.github/scripts/tests/test_documentation_review_workflows.py

@@ -0,0 +1,30 @@
+"""Keep machine generation explicit without losing automatic validation."""
+from pathlib import Path
+import unittest
+
+import yaml
+
+
+ROOT = Path(__file__).resolve().parents[3]
+
+
+class DocumentationReviewWorkflowTests(unittest.TestCase):
+    def workflow(self, name):
+        return yaml.load(
+            (ROOT / '.github/workflows' / name).read_text(encoding='utf-8'),
+            Loader=yaml.BaseLoader,
+        )
+
+    def test_generation_requires_explicit_dispatch(self):
+        triggers = self.workflow('build-web-docs-i18n.yml')['on']
+        self.assertEqual(set(triggers), {'workflow_dispatch'})
+
+    def test_website_changes_keep_automatic_offline_validation(self):
+        triggers = self.workflow('test-i18n.yml')['on']
+        for event in ('pull_request', 'push'):
+            with self.subTest(event=event):
+                self.assertIn('web/**', triggers[event]['paths'])
+
+
+if __name__ == '__main__':
+    unittest.main()