start the download before fetching its artwork

- The artwork step no longer holds up the media: the song goes to the platform
  first and the art is fetched afterwards, in the same foreground window. A
  stalled artwork server can no longer delay a download, and a process death
  during the fetch can no longer lose the download entirely.
- Resuming a queued download after a restart fetches its artwork now too; only a
  fresh download did before.
- The artwork budget is a minute rather than ten seconds, which costs nothing but
  a live coroutine now that nothing waits on it for the media.
- OkHttpArtworkFetcher derives a client with a per-call timeout. A blocking
  OkHttp call is not interrupted by a coroutine timeout, so without it the outer
  budget bounded our wait but not the socket.

app/src/test/kotlin/com/subtracks/data/repo/DownloadRepositoryTest.kt

@@ -46,10 +46,12 @@ class DownloadRepositoryTest {
     private lateinit var dir: File
     private val messages = CopyOnWriteArrayList<String>()
     private val requestedArt = CopyOnWriteArrayList<String>()
+    private val artFetchedAfterTheEngineRequest = CopyOnWriteArrayList<Boolean>()
     private var failArtworkFetch = false
     private val fetcher =
         ArtworkFetcher { url ->
             requestedArt += url
+            artFetchedAfterTheEngineRequest += engine.requests.isNotEmpty()
             if (failArtworkFetch) throw IOException("boom")
             byteArrayOf(1, 2, 3)
         }
@@ -312,6 +314,29 @@ class DownloadRepositoryTest {
             }
         }
 
+    @Test
+    fun theDownloadStartsBeforeItsArtworkIsFetched() =
+        runTest {
+            seedLibrary()
+
+            runBlocking { repository.download(1, "s1") }
+
+            assertTrue(artFetchedAfterTheEngineRequest.isNotEmpty())
+            assertTrue(artFetchedAfterTheEngineRequest.all { it })
+        }
+
+    @Test
+    fun resumingAQueuedDownloadAlsoStoresItsArtwork() =
+        runTest {
+            seedLibrary()
+            db.downloadDao().upsert(SongDownload(1, "s1", DownloadStatus.Queued, engineId = 7))
+
+            runBlocking { repository.reconcile() }
+
+            assertEquals(1, engine.requests.size)
+            assertNotNull(artwork.uri(1, coverArtKey(1, ALBUM_ART, false)))
+        }
+
     @Test
     fun aSongWithoutArtworkStillDownloads() =
         runTest {