fix(social): robot blocks

Blocking an auto-match opponent who is secretly a pooled robot is recorded  instead in a separate `robot_blocks` table.

Now blocking behaves the same in that game (struck name, hidden composer) and lists the blocked opponent under the name you saw, but is recorded only against that game — the disguise holds, the shared robot is never globally blocked, and the matchmaker keeps pairing you with robots (so you can never block yourself out of opponents).

- the shared robot account is never put in `blocks`
- the matchmaker keeps it free and it is not blocked under its other per-game names
- the blocked list and the in-game card still show it by joining that table; an unblock deletes the row

backend/internal/social/blocks.go

@@ -35,15 +35,23 @@ func (svc *Service) Block(ctx context.Context, blockerID, blockedID uuid.UUID) e
 	return nil
 }
 
-// Unblock removes blockerID's block on blockedID and confirms it to the (former)
-// blocker with a user_unblocked event so their open game screens restore the controls
-// and un-strike the name in place. Any friendship the block had been overriding becomes
-// effective again. It is idempotent.
-func (svc *Service) Unblock(ctx context.Context, blockerID, blockedID uuid.UUID) error {
-	if err := svc.store.deleteBlock(ctx, blockerID, blockedID); err != nil {
+// Unblock removes blockerID's block on the given target and confirms it to the (former)
+// blocker with a user_unblocked event so their open game screens restore the controls and
+// un-strike the name in place. The target is either a blocked human's account id (the
+// blocks table) or a robot_blocks row id (a per-game disguised-robot block) — the robot
+// block is tried first, falling back to the human block. Any friendship the block had been
+// overriding becomes effective again. It is idempotent.
+func (svc *Service) Unblock(ctx context.Context, blockerID, target uuid.UUID) error {
+	removed, err := svc.store.deleteRobotBlock(ctx, blockerID, target)
+	if err != nil {
 		return err
 	}
-	svc.pub.Publish(notify.NotificationAccount(blockerID, notify.NotifyUserUnblocked, svc.accountRef(ctx, blockedID)))
+	if !removed {
+		if err := svc.store.deleteBlock(ctx, blockerID, target); err != nil {
+			return err
+		}
+	}
+	svc.pub.Publish(notify.NotificationAccount(blockerID, notify.NotifyUserUnblocked, svc.accountRef(ctx, target)))
 	return nil
 }