feat(login): 调整用户角色选择顺序并更新角色标识

- 调整患者、患者家属和医生角色按钮的显示顺序
- 更新角色标识常量注释以匹配新顺序
- 患者角色由 2 改为 3，患者家属由 3 改为 4，医生由 1 改为 2

src/pages/login/login.vue

@@ -10,9 +10,9 @@
       </view>
 
       <view class="role-section">
-        <button class="role-btn" @click="onSelectRole(2)" :disabled="isLogging">患者</button>
-        <button class="role-btn" @click="onSelectRole(3)" :disabled="isLogging">患者家属</button>
-        <button class="role-btn" @click="onSelectRole(1)" :disabled="isLogging">医生</button>
+        <button class="role-btn" @click="onSelectRole(3)" :disabled="isLogging">患者</button>
+        <button class="role-btn" @click="onSelectRole(4)" :disabled="isLogging">患者家属</button>
+        <button class="role-btn" @click="onSelectRole(2)" :disabled="isLogging">医生</button>
       </view>
 
       <view class="info-text">点击身份后会使用微信登录并向后端发送登录请求。控制台将打印后端返回的 token。</view>
@@ -29,7 +29,7 @@ import CustomNav from '@/components/CustomNav.vue'
 const isLogging = ref(false)
 
 /**
- * role: 1=SYS_ADMIN(医生), 2=PATIENT(患者), 3=PATIENT_FAMILY(患者家属)
+ * role: 2=DOCTOR(医生), 3=PATIENT(患者), 4=PATIENT_FAMILY(患者家属)
  */
 async function onSelectRole(role: number) {
   if (isLogging.value) return