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/state/callPreferences.ts

@@ -35,7 +35,7 @@ export const makeCallPreferencesAtom = (userId: string): CallPreferencesAtom =>
     (key, value) => {
       // Don't persist video state — always resets to off on next load.
       setLocalStorageItem(key, { ...value, video: false });
-    }
+    },
   );
 
   return callPreferencesAtom;