feat(ECR-011): 昵称、首页贴士与档案 Self 唯一/合盘交叉校验

每账号仅一条 self（migration 40902）；合盘只选 TA；账号昵称可改；首页穿衣/颜色/养生贴士。

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/internal/service/profile/service.go

@@ -30,6 +30,9 @@ type CreateInput struct {
 	BirthPlace   *string
 }
 
+// ErrSelfExists is returned when creating a second self profile.
+var ErrSelfExists = errors.New("self profile already exists")
+
 // Create stores a profile for the user.
 func (s *Service) Create(ctx context.Context, userID uuid.UUID, in CreateInput) (*model.Profile, error) {
 	if in.Relation != "self" && in.Relation != "other" {
@@ -38,6 +41,15 @@ func (s *Service) Create(ctx context.Context, userID uuid.UUID, in CreateInput)
 	if in.BirthDate.IsZero() {
 		return nil, errors.New("birth_date required")
 	}
+	if in.Relation == "self" {
+		n, err := s.Repo.CountActiveSelf(ctx, userID)
+		if err != nil {
+			return nil, err
+		}
+		if n > 0 {
+			return nil, ErrSelfExists
+		}
+	}
 	name := in.DisplayName
 	if name == "" {
 		if in.Relation == "self" {