feat(web): "You might like" Home row (#790 web client slice)

The web UI rendered a fixed set of Home sections and had no code for the
server's you_might_like_albums / you_might_like_artists (shipped in
v2026.06.11), so the row was absent in the web client. Adds it, mirroring
the Rediscover block, positioned directly under the system-playlists row.

- types.ts HomePayload: two new slices (server always emits them; web ships
  in lockstep with the server).
- +page.svelte: a "You might like" section (albums + artists scrollers) as the
  first section under the playlists row, with a "still learning your taste"
  empty state for the cold-start/gated case. Reuses existing AlbumCard /
  ArtistCard / HorizontalScrollRow.
- home.test.ts / page.test.ts: mock payloads gain the two fields.

Completes the You-might-like row across all three clients (server already
emits it; Android in v2026.06.11; web here).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/lib/api/home.test.ts

@@ -18,7 +18,9 @@ describe('home client', () => {
       rediscover_albums: [],
       rediscover_artists: [],
       most_played_tracks: [],
-      last_played_artists: []
+      last_played_artists: [],
+      you_might_like_albums: [],
+      you_might_like_artists: []
     };
     (api.get as ReturnType<typeof vi.fn>).mockResolvedValueOnce(fixture);
     const got = await listHome();

web/src/lib/api/types.ts

@@ -342,4 +342,6 @@ export type HomePayload = {
   rediscover_artists:    ArtistRef[];
   most_played_tracks:    TrackRef[];
   last_played_artists:   ArtistRef[];
+  you_might_like_albums:  AlbumRef[];
+  you_might_like_artists: ArtistRef[];
 };