feat(subsonic): wire /rest/scrobble into playevents.Writer

submission=false → play_started (replaces in-memory nowPlayingMap).
submission=true (default) → synthetic completed play. The nowPlayingMap
struct + factory + the nowPlaying field on mediaHandlers are deleted;
play_events WHERE ended_at IS NULL is now the source of truth for
'currently playing,' reachable from M3+ work.

api.Mount now takes the shared *playevents.Writer instead of cfg so
the same writer instance feeds both surfaces.

internal/subsonic/scrobble_test.go

@@ -0,0 +1,119 @@
+package subsonic
+
+import (
+	"context"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/playevents"
+)
+
+func testScrobblePool(t *testing.T) (*pgxpool.Pool, dbq.User, dbq.Track) {
+	t.Helper()
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+	dsn := os.Getenv("MINSTREL_TEST_DATABASE_URL")
+	if dsn == "" {
+		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
+	}
+	if err := db.Migrate(dsn, slog.New(slog.NewTextHandler(io.Discard, nil))); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	pool, err := pgxpool.New(context.Background(), dsn)
+	if err != nil {
+		t.Fatalf("pool: %v", err)
+	}
+	t.Cleanup(pool.Close)
+	if _, err := pool.Exec(context.Background(),
+		"TRUNCATE play_events, skip_events, play_sessions, sessions, users, tracks, albums, artists RESTART IDENTITY CASCADE"); err != nil {
+		t.Fatalf("truncate: %v", err)
+	}
+	q := dbq.New(pool)
+	u, err := q.CreateUser(context.Background(), dbq.CreateUserParams{
+		Username: "tester", PasswordHash: "x", ApiToken: "x", IsAdmin: false,
+	})
+	if err != nil {
+		t.Fatalf("user: %v", err)
+	}
+	a, _ := q.UpsertArtist(context.Background(), dbq.UpsertArtistParams{Name: "X", SortName: "X"})
+	al, _ := q.UpsertAlbum(context.Background(), dbq.UpsertAlbumParams{Title: "X", SortTitle: "X", ArtistID: a.ID})
+	tr, _ := q.UpsertTrack(context.Background(), dbq.UpsertTrackParams{
+		Title: "Y", AlbumID: al.ID, ArtistID: a.ID, FilePath: "/tmp/scrob.flac", DurationMs: 100_000,
+	})
+	return pool, u, tr
+}
+
+func newScrobbleHandlers(pool *pgxpool.Pool) *mediaHandlers {
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	w := playevents.NewWriter(pool, logger, 30*time.Minute, 0.5, 30000)
+	return newMediaHandlers(pool, w)
+}
+
+func TestHandleScrobble_SubmissionFalseInsertsOpenPlayEvent(t *testing.T) {
+	pool, user, track := testScrobblePool(t)
+	m := newScrobbleHandlers(pool)
+
+	q := url.Values{}
+	q.Set("id", uuidToID(track.ID))
+	q.Set("submission", "false")
+	req := httptest.NewRequest(http.MethodGet, "/rest/scrobble?"+q.Encode(), nil)
+	ctx := context.WithValue(req.Context(), userCtxKey, user)
+	w := httptest.NewRecorder()
+	m.handleScrobble(w, req.WithContext(ctx))
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("status = %d", w.Code)
+	}
+	rows, _ := pool.Query(context.Background(),
+		"SELECT id FROM play_events WHERE user_id=$1 AND ended_at IS NULL", user.ID)
+	defer rows.Close()
+	count := 0
+	for rows.Next() {
+		count++
+	}
+	if count != 1 {
+		t.Errorf("open play_events count = %d, want 1", count)
+	}
+}
+
+func TestHandleScrobble_SubmissionTrueWritesCompletedPlay(t *testing.T) {
+	pool, user, track := testScrobblePool(t)
+	m := newScrobbleHandlers(pool)
+
+	q := url.Values{}
+	q.Set("id", uuidToID(track.ID))
+	q.Set("submission", "true")
+	req := httptest.NewRequest(http.MethodGet, "/rest/scrobble?"+q.Encode(), nil)
+	ctx := context.WithValue(req.Context(), userCtxKey, user)
+	w := httptest.NewRecorder()
+	m.handleScrobble(w, req.WithContext(ctx))
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("status = %d", w.Code)
+	}
+	rows, _ := pool.Query(context.Background(),
+		"SELECT ended_at IS NOT NULL FROM play_events WHERE user_id=$1", user.ID)
+	defer rows.Close()
+	closed := 0
+	for rows.Next() {
+		var c bool
+		_ = rows.Scan(&c)
+		if c {
+			closed++
+		}
+	}
+	if closed != 1 {
+		t.Errorf("closed play_events = %d, want 1", closed)
+	}
+}