style(表单): 为家庭格言输入框添加占位符样式

在EditFamily和CreateFamily页面中，为家庭格言输入框添加placeholder-style属性，设置占位符文字颜色为#d1d5db以改善视觉效果

 <!--
  * @Date: 2025-08-27 17:44:53
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-09-16 22:16:21
+ * @LastEditTime: 2025-09-22 10:51:07
  * @FilePath: /lls_program/src/pages/CreateFamily/index.vue
  * @Description: 创建家庭
 -->
@@ -79,6 +79,7 @@
                     type="text"
                     v-model="familyMotto[index]"
                     :placeholder="familyMottoPlaceholder[index]"
+                    placeholder-style="color: #d1d5db;"
                     @input="(e) => handleInputChange(index, e.target.value)"
                     @focus="focusedIndex = index"
                     @blur="handleBlur(index)"

 <!--
  * @Date: 2025-08-27 17:44:53
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-09-16 13:49:51
+ * @LastEditTime: 2025-09-22 10:51:28
  * @FilePath: /lls_program/src/pages/EditFamily/index.vue
  * @Description: 文件描述
 -->
@@ -77,6 +77,7 @@
                     type="text"
                     v-model="familyMotto[index]"
                     :placeholder="familyMottoPlaceholder[index]"
+                    placeholder-style="color: #d1d5db;"
                     @input="(e) => handleInputChange(index, e.target.value)"
                     @focus="focusedIndex = index"
                     @blur="handleBlur(index)"