feat(social): add listening activity, shared rooms and modern chat

services/api/internal/playback/social_activity.go

@@ -0,0 +1,26 @@
+package playback
+
+import (
+	"context"
+	"errors"
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"pipu/api/internal/api/gen"
+	"pipu/api/internal/platform/apperr"
+)
+
+// ReadSocialPlaylist is a projection port for social after live activity authorization.
+// DTO signing and reactions still use the requesting viewer's principal from ctx.
+func (h *Handler) ReadSocialPlaylist(ctx context.Context, id uuid.UUID) (gen.Playlist, error) {
+	var owner uuid.UUID
+	e := h.store.pool.QueryRow(ctx, `SELECT user_id FROM playlists WHERE id=$1`, id).Scan(&owner)
+	if errors.Is(e, pgx.ErrNoRows) {
+		return gen.Playlist{}, apperr.NotFound("playlist.not_found", "playlist not found")
+	}
+	if e != nil {
+		return gen.Playlist{}, e
+	}
+	p, e := h.readPlaylist(ctx, owner, id, false)
+	p.ShareId = nil
+	return p, e
+}