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/repository/auth_repo.go

@@ -97,6 +97,14 @@ func (r *AuthRepo) CreateUserWithPhone(ctx context.Context, phone, hash, nicknam
 	return id, err
 }
 
+// UpdateNickname sets users.nickname (non-empty).
+func (r *AuthRepo) UpdateNickname(ctx context.Context, userID uuid.UUID, nickname string) error {
+	_, err := r.Pool.Exec(ctx, `
+		UPDATE users SET nickname=$2, updated_at=now()
+		WHERE id=$1 AND deleted_at IS NULL`, userID, nickname)
+	return err
+}
+
 // TouchPassword updates stored password hash (open-login record).
 func (r *AuthRepo) TouchPassword(ctx context.Context, userID uuid.UUID, hash string) error {
 	_, err := r.Pool.Exec(ctx, `