Complete client UI i18n migration

Adds client-side i18n support, language settings, translated UI copy, and locale parity coverage.

packages/app/src/components/rewind/use-rewind-agent-mutation.ts

@@ -1,4 +1,5 @@
 import { useCallback } from "react";
+import { useTranslation } from "react-i18next";
 import { useMutation } from "@tanstack/react-query";
 import { useToast } from "@/contexts/toast-context";
 import type { DaemonClient } from "@getpaseo/client/internal/daemon-client";
@@ -25,11 +26,12 @@ export function useRewindAgentMutation(input: UseRewindAgentMutationInput): {
   isPending: boolean;
 } {
   const toast = useToast();
+  const { t } = useTranslation();
   const composerRestore = useRewindComposerRestore();
   const { isPending, mutateAsync } = useMutation({
     mutationFn: async ({ mode }: RewindAgentInput) => {
       if (!input.client || !input.agentId || !input.messageId) {
-        throw new Error("Daemon client not available");
+        throw new Error(t("common.errors.daemonClientUnavailable"));
       }
       await input.client.rewindAgent(input.agentId, input.messageId, mode);
       if (mode !== "files") {
@@ -59,7 +61,7 @@ export function useRewindAgentMutation(input: UseRewindAgentMutationInput): {
       composerRestore?.restoreTextIfComposerEmpty(variables.rewoundText);
     },
     onError: (error) => {
-      toast.error(error instanceof Error ? error.message : "Failed to rewind agent");
+      toast.error(error instanceof Error ? error.message : t("rewind.errors.failed"));
     },
   });