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>

cmd/minstrel/main.go

@@ -14,6 +14,7 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/coverart"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/library"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrconfig"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrrequests"
@@ -146,7 +147,12 @@ func run() error {
 	// import requests and reconciles them against the library. Short-circuits
 	// to no-op when lidarr_config.enabled = false.
 	lidarrCfg := lidarrconfig.New(pool)
-	lidarrReconciler := lidarrrequests.NewReconciler(pool, lidarrCfg, logger.With("component", "lidarr"))
+	// Live-event bus shared between SSE subscribers (api.Mount) and
+	// background workers that publish (reconciler today; scanner later).
+	// Constructed before any service that publishes so they all share the
+	// same instance.
+	bus := eventbus.New()
+	lidarrReconciler := lidarrrequests.NewReconciler(pool, lidarrCfg, logger.With("component", "lidarr"), bus)
 	go lidarrReconciler.Run(ctx)
 
 	// Ensure DataDir exists before any service tries to write into it.
@@ -173,6 +179,7 @@ func run() error {
 	srv := server.New(logger, pool, scanner, subsonic.Config{
 		AllowPlaintextPassword: cfg.Subsonic.AllowPlaintextPassword,
 	}, cfg.Events, cfg.Recommendation, cfg.Storage.DataDir, cfg.Branding, coverEnricher, cfg.Library.CoverArtBackfillCap, coverSettings, scanner, scanCfg, scheduler)
+	srv.Bus = bus
 	playlists.StartSystemPlaylistCron(ctx, pool, logger.With("component", "system_playlist_cron"), cfg.Storage.DataDir)
 	httpServer := &http.Server{
 		Addr:              cfg.Server.Address,