Merge the updated i18n branch (#111) into the Phase 2 integration branch

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MRtGG9ARfqqhma3t85Ro2u

apps/web/e2e/chat-contrast.spec.ts

@@ -221,8 +221,8 @@ test("shell surfaces stay readable in light and dark themes", async ({ page }, t
       inside: true,
     });
     await expectReadable(
-      sidebar.getByRole("button", { name: "Heute", exact: true }),
+      sidebar.getByRole("button", { name: "Today", exact: true }),
-      `${theme}: Heute`,
+      `${theme}: Today`,
       { inside: true },
     );
     await expectReadable(