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/routes/page.test.ts

@@ -13,7 +13,9 @@ vi.mock('$lib/api/home', () => ({
         most_played_tracks: [],
         rediscover_albums: [],
         rediscover_artists: [],
-        last_played_artists: []
+        last_played_artists: [],
+        you_might_like_albums: [],
+        you_might_like_artists: []
       },
       isPending: false,
       isError: false,