chore: upgrade i18next 26, prettier 3, fontsource-variable, domhandler 6, lint-staged 17

- i18next 23->26 + react-i18next 15->17
- prettier 2->3, reformat all files
- replace @fontsource/inter with @fontsource-variable/inter 5, update import path
- domhandler 5->6 (aligns with transitive deps)
- lint-staged 16->17

src/app/components/AccountDataEditor.tsx

@@ -54,7 +54,7 @@ function AccountDataEdit({
 
   const { handleKeyDown, operations, getTarget } = useTextAreaCodeEditor(
     textAreaRef,
-    EDITOR_INTENT_SPACE_COUNT
+    EDITOR_INTENT_SPACE_COUNT,
   );
 
   const [submitState, submit] = useAsyncCallback<void, MatrixError, [string, object]>(submitChange);
@@ -278,7 +278,7 @@ export function AccountDataEditor({
 
   const contentJSONStr = useMemo(
     () => JSON.stringify(data.content, null, EDITOR_INTENT_SPACE_COUNT),
-    [data.content]
+    [data.content],
   );
 
   return (