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/hooks/useTextAreaIntent.ts

@@ -5,7 +5,7 @@ import { Cursor, Intent, Operations, TextArea } from '../plugins/text-area';
 export const useTextAreaIntentHandler = (
   textArea: TextArea,
   operations: Operations,
-  intent: Intent
+  intent: Intent,
 ) => {
   const handler: KeyboardEventHandler<HTMLTextAreaElement> = useCallback(
     (evt) => {
@@ -51,7 +51,7 @@ export const useTextAreaIntentHandler = (
         operations.select(intent.addPreviousLine(cursor));
       }
     },
-    [textArea, operations, intent]
+    [textArea, operations, intent],
   );
 
   return handler;