feat(storage): functional Storage dashboard (§A6)

Replace the "coming soon" stub with a real dashboard wired to
`GET /storage`. modern-sk visuals: a layered disk-capacity gauge (library
share vs other-used vs free), stat tiles (tracks/artists/albums/playtime/
footprint/avg size), per-format size bars, metadata-health badges, source
breakdown, a popularity-weighted top-genres cloud, and playful fun facts.

- types: full `StorageStats` shape + `toStorageStats` snake→camel mapper
- endpoint: re-point `getStorageStats` to `GET /storage` with transform
- lib: `formatLongDuration` for big playtime spans
- i18n: `storage.*` keys (en + ru)
- three list states (loading / error / empty) per the UI invariant

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/api/endpoints/storage.ts

@@ -1,17 +1,16 @@
 import { api } from '../index';
+import { toStorageStats, type RawStorageStats } from '../mappers';
 import type { StorageStats } from '../types';
 
-// NOTE: the backend `/storage` routes are still unimplemented stubs (no body /
-// no schema), and the real paths differ from these placeholders (`GET /storage`,
-// `/storage/duplicates`, `/storage/broken`, `/storage/missing-metadata`,
-// `POST /storage/cleanup`). Re-point paths and add snake→camel mappers (see
-// `mappers.ts`) once the backend defines the storage response shapes; until then
-// these are provisional and unused by the UI.
+// `GET /storage` returns library + disk statistics (§A6). The maintenance
+// routes (`/storage/duplicates`, `/storage/broken`, `/storage/missing-metadata`,
+// `POST /storage/cleanup`) are still backend stubs and unused by the UI.
 
 export const storageApi = api.injectEndpoints({
   endpoints: (build) => ({
     getStorageStats: build.query<StorageStats, void>({
-      query: () => '/storage/stats',
+      query: () => '/storage',
+      transformResponse: (raw: RawStorageStats) => toStorageStats(raw),
       providesTags: ['Storage'],
     }),
     scanStorage: build.mutation<{ jobId: string }, void>({

src/api/mappers.ts

@@ -18,6 +18,7 @@ import type {
   MetadataStatus,
   PaginatedResponse,
   Playlist,
+  StorageStats,
   Track,
   User,
 } from './types';
@@ -200,6 +201,47 @@ export const toPlaylist = (r: RawPlaylist): Playlist => ({
   updatedAt: r.created_at,
 });
 
+interface RawStorageStats {
+  total_tracks: number;
+  total_artists: number;
+  total_albums: number;
+  total_size: number;
+  total_duration_seconds: number;
+  largest_track_size: number;
+  earliest_added: string | null;
+  latest_added: string | null;
+  by_format: { file_format: string; track_count: number; total_size: number }[];
+  by_metadata_status: Record<string, number>;
+  by_source: Record<string, number>;
+  top_genres: { genre: string; track_count: number }[];
+  disk: { total: number; used: number; free: number } | null;
+}
+
+export type { RawStorageStats };
+
+export const toStorageStats = (r: RawStorageStats): StorageStats => ({
+  totalTracks: r.total_tracks,
+  totalArtists: r.total_artists,
+  totalAlbums: r.total_albums,
+  totalSize: r.total_size,
+  totalDurationSeconds: r.total_duration_seconds,
+  largestTrackSize: r.largest_track_size,
+  earliestAdded: r.earliest_added ?? undefined,
+  latestAdded: r.latest_added ?? undefined,
+  byFormat: r.by_format.map((f) => ({
+    fileFormat: f.file_format,
+    trackCount: f.track_count,
+    totalSize: f.total_size,
+  })),
+  byMetadataStatus: r.by_metadata_status,
+  bySource: r.by_source,
+  topGenres: r.top_genres.map((g) => ({
+    genre: g.genre,
+    trackCount: g.track_count,
+  })),
+  disk: r.disk ?? undefined,
+});
+
 /**
  * Translate the backend's `{items,total,limit,offset}` envelope into the UI's
  * `{items,total,page,pageSize,hasMore}`, mapping each element.

src/api/types.ts

@@ -96,12 +96,40 @@ export interface UploadResponse {
   already_exists: boolean;
 }
 
-export interface StorageStats {
-  totalBytes: number;
-  usedBytes: number;
+export interface StorageFormatBreakdown {
+  fileFormat: string;
   trackCount: number;
-  albumCount: number;
-  artistCount: number;
+  totalSize: number;
+}
+
+export interface StorageGenreCount {
+  genre: string;
+  trackCount: number;
+}
+
+/** Capacity of the volume backing the media store. Absent for object-store
+ * backends (S3), which have no fixed disk to report. */
+export interface StorageDiskUsage {
+  total: number;
+  used: number;
+  free: number;
+}
+
+export interface StorageStats {
+  totalTracks: number;
+  totalArtists: number;
+  totalAlbums: number;
+  /** Sum of every track's recorded file size (the library's footprint). */
+  totalSize: number;
+  totalDurationSeconds: number;
+  largestTrackSize: number;
+  earliestAdded?: string;
+  latestAdded?: string;
+  byFormat: StorageFormatBreakdown[];
+  byMetadataStatus: Record<string, number>;
+  bySource: Record<string, number>;
+  topGenres: StorageGenreCount[];
+  disk?: StorageDiskUsage;
 }
 
 export interface User {