docs(settings): improve Metadata settings docs

docs/using-seerr/settings/metadata.md

@@ -0,0 +1,44 @@
+---
+title: Metadata Providers
+description: Configure the metadata providers Seerr uses.
+sidebar_position: 8
+---
+
+# Metadata Providers
+
+Seerr fetches descriptive metadata (titles, descriptions, posters, release dates,
+external IDs, etc.) from a number of third-party providers. The
+**Settings → Metadata Providers** page lets administrators pick which provider
+is used for each media type.
+
+A **Test** button at the top and bottom of the page exercises every configured
+provider and updates the two status badges (`TheMovieDB`, `TheTVDB`). Each badge shows one of:
+
+- **Operational** — the test request succeeded.
+- **Not tested** — no test has been run yet in this session.
+- **Failed** — the test request errored; a toast describes which provider(s)
+  failed so the issue can be resolved without scrolling back up.
+
+## Metadata Provider Selection
+
+This section controls which provider is used for which media type.
+
+### TV series Metadata Provider
+
+Choose between **TheMovieDB** and **TheTVDB** as the source of metadata for TV
+series. TheMovieDB is the default and matches the source used for movies, which
+keeps IDs and artwork consistent across the UI.
+
+### Anime Metadata Provider
+
+Choose between **TheMovieDB** and **TheTVDB** for anime entries.
+
+## Metadata Provider Testing
+
+The **Test** buttons make one request per provider.
+
+*TMDB / TVDB are tested only when selected as the active provider for one of
+the media types.*
+
+If any test fails, an error is shown for that provider and its status badge is
+updated.