feat(#392): publish track-like + request-status events to SSE bus

Slice 2 of #392 — wires the first producers onto the bus that slice 1
built. After this commit, an SSE subscriber sees real events fire:

- track.liked / track.unliked when the user toggles the heart on a track
  (handleLikeTrack / handleUnlikeTrack). Album + artist like events
  intentionally deferred — they're symmetric trivial follow-ups but the
  operator's primary like surface is tracks.
- request.status_changed when a Lidarr request is created, cancelled,
  approved, or rejected. Auto-approve will fire twice (pending then
  approved) in rapid succession, which is semantically correct; client
  invalidation handles that fine.

Events are user-scoped via row.UserID so admin approve/reject route to
the requester, not the admin acting. Helpers live in events_publish.go
so the wire shape (kind names, payload keys) stays in one place — future
producers in slice 3 reuse the same pattern.

events_publish.go is no-op when h.eventbus is nil so tests that
construct handlers without a bus continue to pass.

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

internal/api/admin_requests.go

@@ -125,6 +125,7 @@ func (h *handlers) handleApproveRequest(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	h.publishRequestStatusChanged(row)
 	writeJSON(w, http.StatusOK, requestViewFrom(row))
 }
 
@@ -164,5 +165,6 @@ func (h *handlers) handleRejectRequest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	h.publishRequestStatusChanged(row)
 	writeJSON(w, http.StatusOK, requestViewFrom(row))
 }

internal/api/events_publish.go

@@ -0,0 +1,68 @@
+// Small helpers for posting live events to the SSE bus (#392). Producers
+// call these from their handler success paths so the wire shape stays in
+// one place. Each helper is a no-op when h.eventbus is nil (older callers
+// or tests that don't construct a bus); production always has one.
+
+package api
+
+import (
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/eventbus"
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+// publishLikeEvent broadcasts a track/album/artist like or unlike. The
+// event is scoped to the user (so only their own clients invalidate); the
+// payload includes the entity_type and entity_id so the dispatcher can
+// invalidate the right query keys.
+func (h *handlers) publishLikeEvent(userID, entityID pgtype.UUID, entityType string, liked bool) {
+	if h.eventbus == nil {
+		return
+	}
+	kind := "track.liked"
+	if !liked {
+		kind = "track.unliked"
+	}
+	if entityType == "album" {
+		if liked {
+			kind = "album.liked"
+		} else {
+			kind = "album.unliked"
+		}
+	}
+	if entityType == "artist" {
+		if liked {
+			kind = "artist.liked"
+		} else {
+			kind = "artist.unliked"
+		}
+	}
+	h.eventbus.Publish(eventbus.Event{
+		Kind:   kind,
+		UserID: uuidToString(userID),
+		Data: map[string]any{
+			"entity_type": entityType,
+			"entity_id":   uuidToString(entityID),
+		},
+	})
+}
+
+// publishRequestStatusChanged broadcasts a Lidarr request status flip to
+// the request's original requester so their /requests page reflects the
+// new state without manual refresh. Admin actors (approve / reject) still
+// route to the requester's user_id, not the admin's — the original user
+// is who needs to see the update.
+func (h *handlers) publishRequestStatusChanged(row dbq.LidarrRequest) {
+	if h.eventbus == nil {
+		return
+	}
+	h.eventbus.Publish(eventbus.Event{
+		Kind:   "request.status_changed",
+		UserID: uuidToString(row.UserID),
+		Data: map[string]any{
+			"request_id": uuidToString(row.ID),
+			"status":     string(row.Status),
+			"kind":       string(row.Kind),
+		},
+	})
+}

internal/api/likes.go

@@ -60,6 +60,7 @@ func (h *handlers) handleLikeTrack(w http.ResponseWriter, r *http.Request) {
 		_ = playevents.CaptureContextualLikeIfPlaying(r.Context(), q, user.ID, id, h.logger)
 	}
 	h.logLikeChange(r, syncpkg.EntityLikeTrack, user.ID, id, syncpkg.OpUpsert)
+	h.publishLikeEvent(user.ID, id, "track", true)
 	w.WriteHeader(http.StatusNoContent)
 }
 
@@ -83,6 +84,7 @@ func (h *handlers) handleUnlikeTrack(w http.ResponseWriter, r *http.Request) {
 		// Don't fail the response — soft-delete is best-effort.
 	}
 	h.logLikeChange(r, syncpkg.EntityLikeTrack, user.ID, id, syncpkg.OpDelete)
+	h.publishLikeEvent(user.ID, id, "track", false)
 	w.WriteHeader(http.StatusNoContent)
 }
 

internal/api/requests.go

@@ -175,6 +175,7 @@ func (h *handlers) handleCreateRequest(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	h.publishRequestStatusChanged(row)
 	writeJSON(w, http.StatusCreated, requestViewFrom(row))
 }
 
@@ -254,5 +255,6 @@ func (h *handlers) handleCancelRequest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	h.publishRequestStatusChanged(row)
 	writeJSON(w, http.StatusOK, requestViewFrom(row))
 }