Search Deezer and MusicBrainz together; add preview clips

Search
- Albums and songs search Deezer and MusicBrainz at once and merge the
  results: duplicates keep the Deezer copy, best word matches first.
  Deezer's search misses albums it carries (Death Magnetic) and most game
  soundtracks; MusicBrainz finds them
- MusicBrainz secondary types are shown ("Soundtrack", "Live")
- Settings: Deezer + MusicBrainz (default), Deezer only, MusicBrainz only
- Search results show which service they came from

Previews
- Songs and albums get a play button (cards, rows, detail view, editor,
  and Deezer search results) for a 30-second Deezer clip; albums play
  their most popular track
- Clips are looked up fresh (Deezer URLs expire), cached 10 minutes, and
  streamed through Canon with Range support; hidden lists stay private
- Entries from MusicBrainz or added by hand are matched to Deezer on save
  so they can preview too
- "Play previews" toggle in Settings → Profile

Tests cover merging and title/artist matching; `-tags live` runs checks
against the real services.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/providers/live_test.go

@@ -0,0 +1,64 @@
+//go:build live
+
+// Live checks against the real music services: go test -tags live ./internal/providers
+package providers
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestLiveMusic(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	reg := NewRegistry(func(context.Context) Credentials { return Credentials{} })
+	albums, _ := reg.For(ctx, "album")
+
+	for _, c := range []struct{ query, want string }{
+		{"death magnetic", "Death Magnetic"},
+		{"super mario galaxy soundtrack", "Super Mario Galaxy Original Soundtrack"},
+		{"chrono trigger original soundtrack", "Chrono Trigger Original Soundtrack"},
+	} {
+		res, err := albums.Search(ctx, c.query)
+		if err != nil {
+			t.Fatalf("%s: %v", c.query, err)
+		}
+		found := -1
+		for i, r := range res {
+			if r.Title == c.want {
+				found = i
+				break
+			}
+		}
+		t.Logf("%q → %q at #%d (%s, type %q)", c.query, c.want, found+1, pick(res, found).Provider, pick(res, found).Extra["type"])
+		if found < 0 || found > 2 {
+			t.Errorf("%q: want %q in the top 3", c.query, c.want)
+		}
+	}
+
+	ref, err := reg.MatchDeezer(ctx, "album", "Death Magnetic", "Metallica")
+	t.Logf("Death Magnetic → Deezer %q", ref)
+	if err != nil || !strings.HasPrefix(ref, "album:") {
+		t.Fatalf("match: %q %v", ref, err)
+	}
+	u, err := reg.DeezerPreview(ctx, ref)
+	if err != nil || !strings.HasPrefix(u, "https://") {
+		t.Fatalf("preview: %q %v", u, err)
+	}
+	t.Logf("preview URL host: %s", strings.SplitN(strings.TrimPrefix(u, "https://"), "/", 2)[0])
+
+	song, err := reg.MatchDeezer(ctx, "song", "Dreams", "Fleetwood Mac")
+	t.Logf("Dreams → Deezer %q", song)
+	if err != nil || song == "" {
+		t.Errorf("song match: %q %v", song, err)
+	}
+}
+
+func pick(res []Result, i int) Result {
+	if i < 0 {
+		return Result{}
+	}
+	return res[i]
+}