fix(cfc-frontend): show family relation graph card even with single member

change FamilyRelationGraph v-if from members.length >= 2 to >= 1
so the card displays for families with only 1 member. the canvas
drawing already guards against drawing lines when < 2 members.

cfc-frontend/components/FamilyRelationGraph.vue

@@ -1,6 +1,6 @@
 <template>
-  <!-- 1人不渲染 -->
-  <view class="family-relation-graph" v-if="members && members.length >= 2">
+  <!-- 家庭关系图谱 -->
+  <view class="family-relation-graph" v-if="members && members.length >= 1">
     <!-- Canvas 连线层 -->
     <canvas
       class="graph-canvas"