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/server/server.go

@@ -11,10 +11,13 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/jackc/pgx/v5/pgxpool"
 
+	"time"
+
 	"git.fabledsword.com/bvandeusen/minstrel/internal/api"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/auth"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/library"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/playevents"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/subsonic"
 	"git.fabledsword.com/bvandeusen/minstrel/web"
 )
@@ -45,14 +48,20 @@ func (s *Server) Router() http.Handler {
 	r.Get("/healthz", s.handleHealthz)
 
 	if s.Pool != nil {
-		api.Mount(r, s.Pool, s.Logger, s.EventsCfg)
+		writer := playevents.NewWriter(
+			s.Pool, s.Logger,
+			time.Duration(s.EventsCfg.SessionTimeoutMinutes)*time.Minute,
+			s.EventsCfg.SkipMaxCompletionRatio,
+			s.EventsCfg.SkipMaxDurationPlayedMs,
+		)
+		api.Mount(r, s.Pool, s.Logger, writer)
 		r.Route("/api/admin", func(admin chi.Router) {
 			admin.Use(auth.RequireAdmin(s.Pool))
 			if s.Scanner != nil {
 				admin.Post("/scan", s.handleAdminScan)
 			}
 		})
-		subsonic.Mount(r, s.Pool, s.Logger, s.SubsonicCfg)
+		subsonic.Mount(r, s.Pool, s.Logger, s.SubsonicCfg, writer)
 	}
 
 	spa := web.Handler()