feat(客户端密钥面板): 代理设置支持连通性检测与状态展示

- 代理卡片新增检测按钮：地址有改动时检测输入值（不落库），否则检测/落库已存值
- 状态行展示检测结果（连通正常/失败原因/耗时），颜色区分通过/失败/警示
- 余量无数据时显示"余额查询暂不可用"占位

frontend-vue/src/shared/components/ApiSecretSettingsPanel.vue

@@ -86,12 +86,27 @@
         </div>
       </div>
 
+      <div class="secret-actions">
+        <button
+          type="button"
+          class="check-btn"
+          :disabled="!proxyReady || busy || proxyChecking"
+          @click="runProxyCheck"
+        >
+          {{ proxyChecking ? '检测中...' : (proxyUrl.trim() && proxyDirty ? '检测输入地址' : '检测已存代理') }}
+        </button>
+        <span class="check-result" :class="proxyResultClass">
+          {{ proxyStatusText }}
+        </span>
+      </div>
+
       <div class="secret-meta">
         <span v-if="proxyLoading">正在读取代理配置...</span>
         <span v-else-if="proxyLoadFailed">代理配置读取失败，请关闭弹窗后重试</span>
         <span v-else-if="!proxySupported">代理设置仅在桌面客户端中可用</span>
         <span v-else-if="balanceLoading">正在查询代理余量...</span>
         <span v-else-if="balance">{{ balanceText }}</span>
+        <span v-else>余额查询暂不可用</span>
       </div>
     </section>
   </div>
@@ -151,6 +166,56 @@ const proxyReady = ref(false)
 const proxySupported = ref(false)
 const proxyDirty = ref(false)
 
+const proxyChecking = ref(false)
+const proxyCheckResult = ref<UserApiSecretCheckResult | null>(null)
+const proxyCheckError = ref('')
+
+const proxyStatusText = computed(() => {
+  if (proxyChecking.value) return '正在检测...'
+  if (proxyCheckResult.value) {
+    const latency = proxyCheckResult.value.checkLatencyMs != null ? `（${proxyCheckResult.value.checkLatencyMs}ms）` : ''
+    if (proxyCheckResult.value.checkStatus === 'passed') return `代理连通正常${latency}`
+    return `${proxyCheckResult.value.checkMessage || '代理检测失败'}`
+  }
+  if (proxyCheckError.value) return proxyCheckError.value
+  return ''
+})
+
+const proxyResultClass = computed(() => {
+  const status = proxyCheckResult.value?.checkStatus
+  return {
+    'check-result--ok': status === 'passed',
+    'check-result--fail': status === 'failed',
+    'check-result--warn': status === 'error',
+  }
+})
+
+/** 检测代理连通性：地址有改动时检测输入值（不落库），否则检测/落库已存值并刷新状态展示。 */
+async function runProxyCheck() {
+  if (proxyChecking.value) return
+  const inputValue = proxyUrl.value.trim()
+  const dirty = proxyDirty.value && inputValue
+  proxyChecking.value = true
+  proxyCheckError.value = ''
+  proxyCheckResult.value = null
+  try {
+    proxyCheckResult.value = await checkApiSecret('proxy', dirty ? inputValue : undefined)
+    const result = proxyCheckResult.value
+    if (result.checkStatus === 'failed') {
+      ElMessage.warning(result.checkMessage || '代理不可用')
+    } else if (result.checkStatus === 'error') {
+      ElMessage.warning(result.checkMessage || '暂时无法判定代理可用性')
+    } else {
+      ElMessage.success(dirty ? '输入地址连通正常（未保存）' : '代理连通正常')
+    }
+  } catch (error) {
+    proxyCheckError.value = error instanceof Error ? error.message : '代理检测失败'
+    ElMessage.error(proxyCheckError.value)
+  } finally {
+    proxyChecking.value = false
+  }
+}
+
 const balance = ref<{ surplus: string | null; balance: string | null } | null>(null)
 const balanceLoading = ref(false)