feat(web): AcoustID card on Integrations — key, threshold, coverage by source (M401 #3922)

The card takes the slot of the unimplemented "MusicBrainz overrides"
placeholder. Rows:
- the on switch
- a write-only key field (the stored key is never sent back), with a
  link to register an application
- the minimum score (0.5 to 1)

Below them, recording-id coverage reads as a column: from tags, looked
up, none, and of the none how many are waiting, no match, ambiguous or
failed. There is a "Look up now" button and a folded list of the tracks
the lookup could not settle.

Off, keyless and stopped-short passes are each a visible state with the
reason (rule 164).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/lib/api/admin.ts

@@ -398,6 +398,66 @@ export async function updateLoudnessSettings(s: LoudnessSettings): Promise<Loudn
   return api.put<LoudnessSettings>('/api/admin/library/loudness-settings', s);
 }
 
+// AcoustID recording-id lookup (M401) ---------------------------------------
+
+export type AcoustIDSettings = {
+  enabled: boolean;
+  min_score: number;
+  /** The key itself is never sent back, only whether one is stored. */
+  api_key_set: boolean;
+};
+
+export type AcoustIDOverview = {
+  settings: AcoustIDSettings;
+  /** Switched on and holding a key: the worker will call AcoustID. */
+  ready: boolean;
+  status: { running: boolean; last_pass_at: string | null; problem: string };
+  /** from_tag + from_acoustid + tracks with no MBID = total. */
+  coverage: {
+    total: number;
+    from_tag: number;
+    from_acoustid: number;
+    ambiguous: number;
+    no_match: number;
+    failed: number;
+    pending: number;
+  };
+};
+
+export type AcoustIDUnsettled = {
+  track_id: string;
+  title: string;
+  artist: string;
+  album: string;
+  file_path: string;
+  state: 'ambiguous' | 'failed';
+  best_score: number | null;
+  candidates: number;
+  detail: string | null;
+  looked_up_at: string;
+};
+
+export async function getAcoustID(): Promise<AcoustIDOverview> {
+  return api.get<AcoustIDOverview>('/api/admin/library/acoustid');
+}
+
+/** api_key left out keeps the stored key; an empty string clears it. */
+export async function updateAcoustIDSettings(s: {
+  enabled: boolean;
+  min_score: number;
+  api_key?: string;
+}): Promise<AcoustIDSettings> {
+  return api.put<AcoustIDSettings>('/api/admin/library/acoustid-settings', s);
+}
+
+export async function runAcoustIDLookup(): Promise<void> {
+  await api.post<null>('/api/admin/library/acoustid/run');
+}
+
+export async function listUnsettledAcoustID(): Promise<AcoustIDUnsettled[]> {
+  return api.get<AcoustIDUnsettled[]>('/api/admin/library/acoustid/unsettled');
+}
+
 // Cover-art providers ------------------------------------------------------
 
 export type CoverProviderCapability = 'album_cover' | 'artist_thumb' | 'artist_fanart';