feat(discover): wire A4 search + A5 downloads to backend

Adds DownloadJob/ExternalSearchResult/SourceInfo contract types + mappers, the downloads + search RTKQ endpoints, and the SearchDownloadPage (search external sources, per-result download states) and DownloadsManagerPage (active/history, progress, retry/cancel, poll-while-active). en/ru i18n. Snapshot also bundles in-progress queue/metadata-editor/storage UI work.

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

src/api/endpoints/downloads.ts

@@ -1,30 +1,88 @@
 import { api } from '../index';
-import type { DownloadJob } from '../types';
+import {
+  toDownloadJob,
+  toPage,
+  type RawDownloadJob,
+  type RawPaged,
+} from '../mappers';
+import type {
+  DownloadJob,
+  DownloadRequestResult,
+  PaginatedResponse,
+} from '../types';
 
-// NOTE: the backend `/downloads` routes are still unimplemented stubs (they
-// return no body / no schema). The request shapes below are provisional and the
-// responses will need the same snake→camel mapper treatment as library/playlists
-// (see `mappers.ts`) once the backend defines DownloadJob's wire format. Do not
-// wire these into the UI until then.
+interface ListParams {
+  status?: DownloadJob['status'];
+  /** Only the current user's jobs (backend `mine=true`). */
+  mine?: boolean;
+  page?: number;
+  pageSize?: number;
+}
+
+interface RawCreateResponse {
+  already_in_library: boolean;
+  track_id: string | null;
+  job: RawDownloadJob | null;
+}
 
 export const downloadsApi = api.injectEndpoints({
   endpoints: (build) => ({
     getDownloads: build.query<
-      DownloadJob[],
-      { status?: DownloadJob['status'] } | void
+      PaginatedResponse<DownloadJob>,
+      ListParams | void
     >({
-      query: (params) => ({ url: '/downloads', params: params ?? {} }),
-      providesTags: ['Download'],
+      query: (params) => {
+        const p = params ?? {};
+        const size = p.pageSize ?? 50;
+        return {
+          url: '/downloads',
+          params: {
+            status: p.status,
+            mine: p.mine ? true : undefined,
+            limit: size,
+            offset: ((p.page ?? 1) - 1) * size,
+          },
+        };
+      },
+      transformResponse: (raw: RawPaged<RawDownloadJob>) =>
+        toPage(raw, toDownloadJob),
+      providesTags: (result) =>
+        result
+          ? [
+              ...result.items.map(({ id }) => ({
+                type: 'Download' as const,
+                id,
+              })),
+              'Download',
+            ]
+          : ['Download'],
     }),
-    addDownload: build.mutation<
-      DownloadJob,
-      {
-        url: string;
-        metadata?: { title?: string; artist?: string; album?: string };
-      }
+    getDownload: build.query<DownloadJob, string>({
+      query: (id) => `/downloads/${id}`,
+      transformResponse: (raw: RawDownloadJob) => toDownloadJob(raw),
+      providesTags: (_r, _e, id) => [{ type: 'Download', id }],
+    }),
+    /** Request a download of a discovered item (§A4 "Download to library"). */
+    createDownload: build.mutation<
+      DownloadRequestResult,
+      { source: string; sourceId: string; query?: string }
     >({
-      query: (body) => ({ url: '/downloads', method: 'POST', body }),
-      invalidatesTags: ['Download'],
+      query: (body) => ({
+        url: '/downloads',
+        method: 'POST',
+        body: {
+          source: body.source,
+          source_id: body.sourceId,
+          query: body.query,
+        },
+      }),
+      transformResponse: (raw: RawCreateResponse): DownloadRequestResult => ({
+        alreadyInLibrary: raw.already_in_library,
+        trackId: raw.track_id ?? undefined,
+        job: raw.job ? toDownloadJob(raw.job) : undefined,
+      }),
+      // A completed dedup can surface an existing library track; refresh both.
+      invalidatesTags: ['Download', 'Track'],
     }),
     cancelDownload: build.mutation<void, string>({
       query: (id) => ({ url: `/downloads/${id}`, method: 'DELETE' }),
@@ -32,7 +90,8 @@ export const downloadsApi = api.injectEndpoints({
     }),
     retryDownload: build.mutation<DownloadJob, string>({
       query: (id) => ({ url: `/downloads/${id}/retry`, method: 'POST' }),
-      invalidatesTags: ['Download'],
+      transformResponse: (raw: RawDownloadJob) => toDownloadJob(raw),
+      invalidatesTags: (_r, _e, id) => [{ type: 'Download', id }, 'Download'],
     }),
   }),
   overrideExisting: false,
@@ -40,7 +99,8 @@ export const downloadsApi = api.injectEndpoints({
 
 export const {
   useGetDownloadsQuery,
-  useAddDownloadMutation,
+  useGetDownloadQuery,
+  useCreateDownloadMutation,
   useCancelDownloadMutation,
   useRetryDownloadMutation,
 } = downloadsApi;