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/test/ui/small_screen_overflow_test.dart

@@ -40,7 +40,14 @@ void main() {
   // iPhone-SE-class logical viewport: narrow AND short, where clipping shows.
   const small = Size(320, 568);
   // The locales whose strings are longest — English rarely overflows first.
-  const longLocales = [AppLocale.es, AppLocale.pt, AppLocale.ast];
+  // German is included for its long compound nouns; French for its verbosity.
+  const longLocales = [
+    AppLocale.es,
+    AppLocale.pt,
+    AppLocale.ast,
+    AppLocale.de,
+    AppLocale.fr,
+  ];
 
   setUpAll(() => PackageInfo.setMockInitialValues(
         appName: 'Tane',