The TV discover page's title sort sent `sort_by=original_title.*` to `/discover/tv`, which is a
movie-only value. TMDB silently ignores invalid `sort_by` parameters and returns its default
popularity order, so sorting series by title did nothing. Sort options are now split per media type
and validated at the route (previously any string was cast and forwarded unchecked), and TV title
sorting uses `original_name.*`.
fix#3304