feat(i18n): add French and German translations

Full fr/de translations of the app (625 keys each), wired into the
Settings language picker and the small-screen overflow test. Material
ships fr/de localizations, so chrome resolves natively.

apps/app_seeds/lib/ui/settings_screen.dart

@@ -50,6 +50,16 @@ class SettingsScreen extends StatelessWidget {
             selected: current == AppLocale.pt,
             onTap: () => pick(AppLocale.pt),
           ),
+          _LanguageTile(
+            label: t.settings.langFr,
+            selected: current == AppLocale.fr,
+            onTap: () => pick(AppLocale.fr),
+          ),
+          _LanguageTile(
+            label: t.settings.langDe,
+            selected: current == AppLocale.de,
+            onTap: () => pick(AppLocale.de),
+          ),
           ListTile(
             leading: const Icon(Icons.smartphone_outlined),
             title: Text(t.settings.systemLanguage),