feat(explore): offer the autotag match on the album page

The complaint was having to notice the metadata was missing, then go
and hunt the album down on the Autotag page. The album page now says it
while you are looking at the thing: "MusicBrainz has a match for this
album: <release> by <artist>", with Apply tags and Review in Autotag.

Four things about it are load-bearing.

**Applying is offered only where it would do the whole album.** A
tagging group is a folder, so a multi-disc album is several, and one
button that applied to the best-scoring group would leave the album
holding a mix of old and new tags — the exact case the app's Blocking
notification level exists for. `groupCount` is the test, and the answer
there is review rather than apply.

**It rewrites files, so it asks.** `confirmAction()` with an impact
line that says it cannot be undone and that nothing is moved or
deleted, because "rewrites your files" reads worse than it is. The
apply goes through `ApplyAsync`, the registered-job path, so progress
belongs to the jobs indicator and this page does not grow a second one
— what it owes the user is the acknowledgement, because the button is
here. The suggestion clears itself on success rather than inviting a
second click while the job runs.

**The banner does not quote a percentage.** The backend has a score and
deliberately keeps it out of the sentence: 0.95 reads as a probability
and is not one. Which release it is, is the part a person can judge.

**"Review in Autotag" lands on that album.** The queue is sorted by
score so the intended folder is often near the top, and "often" is a
link that sometimes opens a different album. Autotag is a cached
primary view, so there is no construction to hand a payload to: the
request goes on as an attribute and the view *consumes* it, or every
later visit would reopen a folder the user finished with long ago.

`ICON_AUTOTAG` joins the vocabulary at the same time, on the rule
`ICON_PLAYLIST` was chosen by — an icon names the noun it acts on, so a
suggestion pointing at Autotag wears the Autotag destination's own
mark. It was written inline in the sidebar; two call sites is where a
name stops being one component's detail, so the sweep governs it now.

Verified against the running app with a staged match: the banner, the
confirm dialog's wording, and the navigation landing on the right
folder with the attribute consumed.

Closes #28

frontend/src/utils/icon-language.ts

@@ -80,6 +80,17 @@ export const ICON_REQUESTED = 'solid/bookmark';
  */
 export const ICON_IN_LIBRARY = 'check';
 
+/**
+ * The autotagger, and a match it is offering.
+ *
+ * The same icon as the Autotag destination in the sidebar, on the rule
+ * `ICON_PLAYLIST` was chosen by: an icon names the noun it acts on, so
+ * a suggestion on the album page wears the mark of the page it would
+ * send you to. Governed from the moment there were two call sites,
+ * which is when a name stops being a detail of one component.
+ */
+export const ICON_AUTOTAG = 'tag';
+
 /**
  * Something is being fetched right now.
  *