feat(core,meta,app,android,ios,cli): TVmaze for the shows AniList does not have

With AniList chosen, a title AniList has no match for is now searched on
TVmaze, keyless, before it is given up on. One provider for the whole library
left live-action shows in a share of anime unmatched, and switching to TMDB
would have dropped every AniList match, chain and shelf.

The service holds a chain of providers. A match is stored under the provider
that gave it, and enrichment and refreshes go to that provider; a miss is
stored under the last provider asked, and is_fresh only trusts a miss from the
end of the chain, so AniList misses stored before this are asked again at once.
A provider failure still ends the lookup instead of falling through.

The hand matcher searches every provider in the chain and labels each result
with its source. TVmaze is never offered in the settings and is not asked
about titles known to be films.

docs/USER_GUIDE.md

@@ -65,9 +65,10 @@ Click a title to open its page. **Esc** goes back.
 - **Resume S01E03 · 12:04** continues where you stopped. **Start over** plays the episode from
   the beginning.
 - **Download show** keeps every episode on this device. See [Downloads](#downloads).
-- **Match…** opens the matcher, where you choose which AniList or TMDB entry the title is. Use it
-  when the app guessed wrong or did not guess at all. A match you pick is never replaced.
-- **More on AniList** (or TMDB) opens the title's page there.
+- **Match…** opens the matcher, where you choose which AniList, TVmaze or TMDB entry the title
+  is. Each result names the site it came from. Use it when the app guessed wrong or did not guess
+  at all. A match you pick is never replaced.
+- **More on AniList** (or TVmaze, or TMDB) opens the title's page there.
 - Each season has **Mark season watched** and **Download season**.
 - Each episode shows a tick when you have watched it. Right-click an episode and choose **Mark
   watched up to here** to tick it and every episode before it.
@@ -220,6 +221,8 @@ a video that is playing changes at once.
 **Posters and descriptions**
 
 - Off by default. When it is on, the app sends the names of your titles to the provider you pick:
-  **AniList** (no key needed) or **TMDB** (needs a free API key). See [Privacy](PRIVACY.md).
+  **AniList** (no key needed) or **TMDB** (needs a free API key). With AniList, a title it does
+  not have, such as a live-action show, is looked up on **TVmaze** next, which needs no key
+  either. See [Privacy](PRIVACY.md).
 - **Match the library** looks up new titles now. **Match everything again** looks up every title,
   except those you matched by hand.