A new Discover rail listing what the user last FULLY watched, newest first: a movie as its
own card, a show as the specific EPISODE watched (carrying its show title via leaf_card). Sits
above Recently added. Movies honour the sidebar filters like the other rails; episodes carry no
filterable metadata so they don't. Clicking a card plays it (the existing onCard path already
routes episodes to the player). Bilingual heading added.
Verified live: the rail renders watched movies + episodes with Watched badges.
Gate: tsc/lint/knip/prettier clean, 423 vitest; backend ruff clean, 13 discover tests (+ a
recently-watched movie+episode assertion).