feat(explore): give the album page a primary action that tells the truth

H-13: no Play, no Shuffle, no Add to queue on the album header. The
reason it is not just three buttons is that explore-album-details is a
catalog page — there is no library-side album detail page at all — so
the album shown may be wholly the user's, partly theirs, or not theirs.
A Play button that plays 7 of a 40-track release under a label saying
'Play' is the page lying about what is owned, so the button says which:
'Play' when all of it is owned, 'Play 7 of 12' when some is, and no
play button at all when none is.

albumLibraryStatus() stays as it was — four claims of decreasing
confidence OR'd into one tick, the weakest firing when a single
recording matches. That is a fine answer to 'is any of this mine' and a
useless basis for a button, so ownership() counts the displayed
tracklist instead.

GetFilePathsByRecordingMBIDs is the catalog-side sibling of
GetFilePathsByAlbums: one query, paths only, grouped so the caller
keeps the tracklist's order. It is keyed on recording MBID because that
is how the backend decides a track is inLibrary, and because
MBTrack.LocalID is declared and never written by anything. The local
album id is preferred where there is one — a library-only album has no
MBIDs at all, and keying on them alone queued nothing.

The ticks also get the legend H-13 asks for. They were never unlabelled
— the indicator has carried a title and aria-label all along — but a
sighted user got a column of green circles and no key.

frontend/wailsjs/go/library/Library.d.ts

@@ -47,6 +47,8 @@ export function GetFilePathsByAlbums(arg1:Array<number>,arg2:number):Promise<Rec
 
 export function GetFilePathsByGenres(arg1:Array<string>,arg2:number):Promise<Record<string, Array<string>>>;
 
+export function GetFilePathsByRecordingMBIDs(arg1:Array<string>,arg2:number):Promise<Record<string, Array<string>>>;
+
 export function GetRemovalImpact(arg1:number):Promise<library.RemovalImpact>;
 
 export function GetScanQueueLength():Promise<number>;

frontend/wailsjs/go/library/Library.js

@@ -86,6 +86,10 @@ export function GetFilePathsByGenres(arg1, arg2) {
   return window['go']['library']['Library']['GetFilePathsByGenres'](arg1, arg2);
 }
 
+export function GetFilePathsByRecordingMBIDs(arg1, arg2) {
+  return window['go']['library']['Library']['GetFilePathsByRecordingMBIDs'](arg1, arg2);
+}
+
 export function GetRemovalImpact(arg1) {
   return window['go']['library']['Library']['GetRemovalImpact'](arg1);
 }