Wire up i18n in both apps

Initialize i18n via initI18n() in both root.tsx files and replace all
hardcoded user-facing strings with useTranslation() calls. Adds missing
translation keys for planner (profiles, connection states, save flow)
and journal (auth pages, route management, passkey prompts).

Both English and German translations are complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/planner/app/components/ExportButton.tsx

@@ -1,10 +1,13 @@
 import { useCallback } from "react";
+import { useTranslation } from "react-i18next";
 import * as Y from "yjs";
 import type { YjsState } from "~/lib/use-yjs";
 import { generateGpx } from "@trails-cool/gpx";
 import type { TrackPoint } from "@trails-cool/gpx";
 
 export function ExportButton({ yjs }: { yjs: YjsState }) {
+  const { t } = useTranslation("planner");
+
   const handleExport = useCallback(() => {
     // Get waypoints from Yjs
     const waypoints = yjs.waypoints.toArray().map((yMap: Y.Map<unknown>) => ({
@@ -51,7 +54,7 @@ export function ExportButton({ yjs }: { yjs: YjsState }) {
       onClick={handleExport}
       className="rounded bg-gray-100 px-3 py-1 text-sm text-gray-700 hover:bg-gray-200"
     >
-      Export GPX
+      {t("exportGpx")}
     </button>
   );
 }