feat(#392): lidarr reconciler publishes request.status_changed on complete

Slice 3b — extends event publishing to background workers.

When the reconciler matches an approved Lidarr request against the
library and flips it to 'completed', it now publishes a
request.status_changed event scoped to the original requester so their
/requests page invalidates without polling. Three call sites — one per
kind (artist / album / track) — capture the completed row instead of
discarding it so the publish has the user_id.

Bus plumbing: the reconciler runs in cmd/minstrel/main.go which
constructs services before server.New is called. Moved bus
construction into main; the Server struct gained a Bus field that
Router() reads, falling back to a fresh local instance when nil
(test contexts). Result: one bus per process shared by every
publisher and the SSE subscriber endpoint.

reconciler.go inlines a uuid->string helper rather than reaching into
internal/api for one — avoids a back-edge dependency.

Test compat: 9 NewReconciler call sites in reconciler_integration_test.go
get `nil` for the new bus param. The reconciler's publishCompleted helper
is a no-op when the bus is nil so tests that don't care about events
keep passing.

Scanner producer (scan.progress) deferred to slice 3c — needs more
thought about which lifecycle transitions warrant events vs. flood the
stream.

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

internal/server/server.go

@@ -80,6 +80,10 @@ type Server struct {
 	LibraryScanner      *library.Scanner
 	ScanCfg             library.RunScanConfig
 	Scheduler           *library.Scheduler
+	// Bus is the live-event bus shared with background workers (the
+	// lidarr reconciler, scan scheduler) constructed in cmd/minstrel/main.go.
+	// When nil, Router() constructs a local fallback (test contexts).
+	Bus *eventbus.Bus
 }
 
 func New(logger *slog.Logger, pool *pgxpool.Pool, scanner ScanTrigger, subCfg subsonic.Config, eventsCfg config.EventsConfig, recCfg config.RecommendationConfig, dataDir string, brandingCfg config.BrandingConfig, coverEnricher *coverart.Enricher, coverArtBackfillCap int, coverSettings *coverart.SettingsService, libraryScanner *library.Scanner, scanCfg library.RunScanConfig, scheduler *library.Scheduler) *Server {
@@ -119,11 +123,16 @@ func (s *Server) Router() http.Handler {
 		playlistsSvc := playlists.NewService(s.Pool, s.Logger, s.DataDir)
 		smtpSender := mailer.NewSMTPSender(s.Pool, s.Logger.With("component", "mailer"))
 		// Live-event bus for SSE subscribers (#392). Constructed per-process;
-		// future producers in playevents / lidarrrequests / scanner / etc.
-		// will publish into the same instance. Slice 1 ships with the
-		// subscriber endpoint (/api/events/stream) only — producers wire up
-		// in later slices.
-		bus := eventbus.New()
+		// producers in playevents / lidarrrequests / scanner publish into
+		// the same instance. Background workers (lidarr reconciler, scan
+		// scheduler) live in cmd/minstrel/main.go where they're constructed
+		// before Router() runs; they read s.Bus directly so they share this
+		// process's bus. When Router() runs before main set the bus (tests,
+		// or future contexts) we fall back to a fresh local instance.
+		bus := s.Bus
+		if bus == nil {
+			bus = eventbus.New()
+		}
 		api.Mount(r, s.Pool, s.Logger, writer, s.RecommendationCfg, lidarrCfg, lidarrReqs, lidarrQuar, tracksSvc, playlistsSvc, s.CoverEnricher, s.CoverArtBackfillCap, s.CoverSettings, s.LibraryScanner, s.ScanCfg, s.Scheduler, s.DataDir, smtpSender, bus)
 		// /api/admin/scan is the only admin route owned by the server package
 		// (it needs the Scanner). Register it as a single inline-middleware