feat(frontend): add french language file

also expanded translation coverage (still lots to do!)

server/utils/typeHelpers.ts

@@ -0,0 +1,17 @@
+import type {
+  TmdbMovieResult,
+  TmdbTvResult,
+  TmdbPersonResult,
+} from '../api/themoviedb';
+
+export const isMovie = (
+  movie: TmdbMovieResult | TmdbTvResult | TmdbPersonResult
+): movie is TmdbMovieResult => {
+  return (movie as TmdbMovieResult).title !== undefined;
+};
+
+export const isPerson = (
+  person: TmdbMovieResult | TmdbTvResult | TmdbPersonResult
+): person is TmdbPersonResult => {
+  return (person as TmdbPersonResult).known_for !== undefined;
+};