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/BackupRestore.tsx

@@ -157,7 +157,7 @@ export function BackupRestoreTile({ crypto }: BackupRestoreTileProps) {
           setRestoreProgress(progress);
         },
       });
-    }, [crypto, setRestoreProgress])
+    }, [crypto, setRestoreProgress]),
   );
 
   const handleRestore = () => {