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/useRelations.ts

@@ -3,7 +3,7 @@ import { RelationsEvent, type Relations } from 'matrix-js-sdk/lib/models/relatio
 
 export const useRelations = <T>(
   relations: Relations,
-  getRelations: (relations: Relations) => T
+  getRelations: (relations: Relations) => T,
 ) => {
   const [data, setData] = useState(() => getRelations(relations));