feat(api): DELETE /api/admin/tracks/{id} for M7 #372

Admin-only handler. Calls tracks.RemoveTrack with the unmonitor flag
parsed from the query string. ErrNotFound -> 404; everything else
unexpected -> 500. Lidarr-side failures during unmonitor flow as
lidarr_unmonitor_failed: true in the success envelope (non-fatal —
the file + DB delete already completed).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/api/api.go

@@ -17,12 +17,13 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrquarantine"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrrequests"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/playevents"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/tracks"
 )
 
 // Mount attaches /api/* handlers to r. Public endpoints (login) are outside
 // RequireUser; everything else is gated by the middleware. The events writer
 // is shared with the Subsonic mount so /rest/scrobble feeds the same store.
-func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playevents.Writer, recCfg config.RecommendationConfig, lidarrCfg *lidarrconfig.Service, lidarrReqs *lidarrrequests.Service, lidarrQuar *lidarrquarantine.Service) {
+func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playevents.Writer, recCfg config.RecommendationConfig, lidarrCfg *lidarrconfig.Service, lidarrReqs *lidarrrequests.Service, lidarrQuar *lidarrquarantine.Service, tracksSvc *tracks.Service) {
 	rng := rand.New(rand.NewSource(rand.Int63()))
 	h := &handlers{
 		pool: pool, logger: logger, events: events, recCfg: recCfg,
@@ -30,6 +31,7 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 		lidarrCfg:        lidarrCfg,
 		lidarrRequests:   lidarrReqs,
 		lidarrQuarantine: lidarrQuar,
+		tracks:           tracksSvc,
 	}
 
 	r.Route("/api", func(api chi.Router) {
@@ -93,6 +95,8 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 				admin.Post("/quarantine/{track_id}/delete-file", h.handleDeleteQuarantineFile)
 				admin.Post("/quarantine/{track_id}/delete-via-lidarr", h.handleDeleteQuarantineViaLidarr)
 				admin.Get("/quarantine/actions", h.handleListQuarantineActions)
+
+				admin.Delete("/tracks/{id}", h.handleRemoveTrack)
 			})
 		})
 	})
@@ -107,4 +111,5 @@ type handlers struct {
 	lidarrCfg        *lidarrconfig.Service
 	lidarrRequests   *lidarrrequests.Service
 	lidarrQuarantine *lidarrquarantine.Service
+	tracks           *tracks.Service
 }