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/useFilePasteHandler.ts

@@ -7,5 +7,5 @@ export const useFilePasteHandler = (onPaste: (file: File[]) => void): ClipboardE
       const files = getDataTransferFiles(evt.clipboardData);
       if (files) onPaste(files);
     },
-    [onPaste]
+    [onPaste],
   );