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/METADATA.md

@@ -45,7 +45,7 @@ good. What hung off it was not:
 |---|---|---|
 | **AniList** GraphQL | none | Identity. Search, every alias, cover art, relations (`SEQUEL`, `PREQUEL`, `SIDE_STORY`…), studios, staff, tags, format, season, popularity, next airing episode, the MAL id. |
 | **ani.zip** `api.ani.zip/mappings?anilist_id=` | none | Everything AniList lacks, per AniList id: TVDB season, episode and absolute numbers; episode titles in several languages; TVDB synopses; 16:9 stills; air dates; runtime. Series art: TVDB **fanart at 1920×1080**, poster, banner, logo. Cross-ids for MAL, AniDB, TVDB, TMDB, Kitsu, IMDb. A community service — cache what it says. |
-| **TMDB** | free key | Film backdrops and logos; live-action TV. Already implemented. |
+| **TMDB** | free key | Film backdrops and logos; live-action TV. Chosen as the provider, or with AniList chosen, asked by id for art alone. |
 | **TVmaze** | none | Live-action TV: episodes with 16:9 stills and runtimes, network, status, full-HD backgrounds. No films; its "typography" art is a JPEG, so no logos. In use after AniList. |
 | **AniSkip** | none | Opening and ending timestamps by MAL id and episode. |
 | **Jikan** (MAL) | none | Filler and recap flags. Timed out when tried; optional. |
@@ -225,6 +225,21 @@ names its episode in dotted words, and `naming::episode_title` now reads them,
 stopping at the first release tag. A dotted run that no tag ends is not taken.
 This is the fallback for a title no provider has.
 
+**Film art from TMDB by id (done).** TVDB has no films, so ani.zip has no
+fanart or logo for one, and seventeen of the library's titles — nearly all
+films — had nothing wide to draw. ani.zip does give the TMDB id
+(`mappings.themoviedb_id`, with `mappings.type` saying whether it is a film's
+or a show's). 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 backdrop without lettering is preferred, and a
+PNG logo in the viewer's language, then English. An OVA's or a special's id is
+left alone, since TMDB files those either way. A failure there is logged and
+the enrichment stored without the art, rather than lost over decoration.
+
+With TMDB itself chosen, enrichment now makes the same request for the logo,
+and backdrops are fetched at `w1280` rather than `w780`, since they fill the
+width of the title page.
+
 Still to do:
 
 - **Local matching** against the offline database, so only ids leave the