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/auth_test.go

@@ -26,6 +26,7 @@ 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"
 )
 
 // testHandlers spins up a handlers instance against MINSTREL_TEST_DATABASE_URL.
@@ -60,7 +61,11 @@ func testHandlers(t *testing.T) (*handlers, *pgxpool.Pool) {
 	lidarrCfg := lidarrconfig.New(pool)
 	lidarrReqs := lidarrrequests.NewService(pool, lidarrCfg, nil, nil)
 	lidarrQuar := lidarrquarantine.NewService(pool, lidarrCfg, nil)
-	h := &handlers{pool: pool, logger: logger, events: w, recCfg: recCfg, rng: func() float64 { return 0.5 }, lidarrCfg: lidarrCfg, lidarrRequests: lidarrReqs, lidarrQuarantine: lidarrQuar}
+	// tracks.Service has no Lidarr unmonitorer in tests by default; the
+	// admin-tracks tests below override h.tracks via installTracksLidarrStub
+	// when they need a stubbed Lidarr.
+	tracksSvc := tracks.NewService(pool, logger, nil)
+	h := &handlers{pool: pool, logger: logger, events: w, recCfg: recCfg, rng: func() float64 { return 0.5 }, lidarrCfg: lidarrCfg, lidarrRequests: lidarrReqs, lidarrQuarantine: lidarrQuar, tracks: tracksSvc}
 	return h, pool
 }