feat(meta,app,android,ios,cli): film backdrops and logos from TMDB by id

TVDB has no films, so ani.zip has no fanart or logo for one, and most of
the titles in a real library with nothing wide to draw were films. ani.zip
does name the TMDB entry of every AniList match. With a TMDB key stored
and AniList chosen, an entry left without a backdrop or a logo is asked
for /{movie,tv}/{id}/images: one request, by id, so no title name goes to
TMDB. A bare backdrop and a PNG logo in the viewer's language are
preferred, and a failure there only costs the art.

The TMDB key field is now offered with either provider, labelled optional
with AniList. TMDB as the provider fetches its logo the same way, and
backdrops at w1280 rather than w780. A forced run re-enriches hand-picked
titles too, so saving a key and matching everything again reaches them.

docs/PRIVACY.md

@@ -10,6 +10,7 @@ and to nothing else unless you turn on posters and descriptions. This page lists
 | Proton | Requests for the shares you added and, if you signed in, your account's Drive | Always |
 | AniList and ani.zip, or TMDB | The names of the titles in your library, and the ids of matched titles | Only with **Posters and descriptions** on |
 | TVmaze | With AniList chosen: the names of the titles AniList has no match for, and the ids of those TVmaze matched | Only with **Posters and descriptions** on |
+| TMDB, with AniList chosen | The TMDB ids of matched titles that have no wide picture or logo yet. Never a title's name | Only with **Posters and descriptions** on and a TMDB key saved |
 
 Nothing else leaves your device. There is no telemetry, no crash reporting and no update check.