feat(daemon): refresh metadata on add

The metadata lane runs daily, so a series added a moment ago showed no
seasons for up to 24 hours and a movie had no digital release date —
the field §6.2 gates targeted search on.

AppState now carries a MetadataCommand channel alongside the movie,
episode and season ones. Both create handlers send on it after the row
is committed, and a new daemon lane drains it. Its own task rather than
an arm of manual::run: a refresh against TMDB can take a while and must
not sit in front of an operator's manual search.

The add never waits on TMDB and never fails because of it. A refresh
that fails leaves metadata_refreshed_at NULL, which is what the daily
sweep already treats as due, so the title is retried rather than lost.
A command naming a title deleted in between finds no row and does
nothing. METADATA_INTERVAL is unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

crates/arr-api/src/lib.rs

@@ -40,7 +40,8 @@ pub use series::{
     UpdateSeason, UpdateSeries,
 };
 pub use state::{
-    AppState, EpisodeCommand, MovieCommand, SeasonCommand, Upstreams, DEFAULT_TMDB_URL,
+    AppState, EpisodeCommand, MetadataCommand, MovieCommand, SeasonCommand, Upstreams,
+    DEFAULT_TMDB_URL,
 };
 pub use trailer::{Trailer, TrailerKind};