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/subsonic.go

@@ -11,15 +11,17 @@ import (
 
 	"github.com/go-chi/chi/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/playevents"
 )
 
 // Mount attaches Subsonic handlers at /rest on r. Endpoints are exposed at
 // both /rest/foo and /rest/foo.view because client conventions vary. Both
 // GET and POST are accepted; Subsonic's auth params live in the query string
 // either way.
-func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, cfg Config) {
+func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, cfg Config, events *playevents.Writer) {
 	b := &browseHandlers{pool: pool}
-	m := newMediaHandlers(pool)
+	m := newMediaHandlers(pool, events)
 	r.Route("/rest", func(sub chi.Router) {
 		sub.Use(Middleware(pool, cfg))
 		register(sub, "/ping", handlePing)