feat: ProxyNode 代理节点管理系统与 OpenAI Responses API 解析增强

ProxyNode 系统：新增 aether-proxy（Rust）海外 VPS 代理组件，后端实现节点注册/心跳/
HMAC 认证/健康检测调度器/模块化集成，前端新增代理节点管理页面。ProxyConfig 支持
node_id 模式，http_client 支持 HMAC 签名代理 URL 构建与 TTL 缓存。

OpenAI CLI 解析器：适配 Responses API 格式，支持 input_tokens/output_tokens 提取、
output[].content[].text 文本解析、response.completed 流式事件 usage 嵌套结构。

frontend/src/stores/proxy-nodes.ts

@@ -0,0 +1,50 @@
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import { proxyNodesApi, type ProxyNode } from '@/api/proxy-nodes'
+
+export const useProxyNodesStore = defineStore('proxy-nodes', () => {
+  const nodes = ref<ProxyNode[]>([])
+  const total = ref(0)
+  const loading = ref(false)
+  const error = ref<string | null>(null)
+
+  async function fetchNodes(params?: { status?: string }) {
+    loading.value = true
+    error.value = null
+
+    try {
+      const data = await proxyNodesApi.listProxyNodes({ ...params, limit: 1000 })
+      nodes.value = data.items
+      total.value = data.total
+    } catch (err: any) {
+      error.value = err.response?.data?.error?.message || err.response?.data?.detail || '获取代理节点列表失败'
+    } finally {
+      loading.value = false
+    }
+  }
+
+  async function deleteNode(nodeId: string) {
+    loading.value = true
+    error.value = null
+
+    try {
+      await proxyNodesApi.deleteProxyNode(nodeId)
+      nodes.value = nodes.value.filter(n => n.id !== nodeId)
+      total.value = Math.max(0, total.value - 1)
+    } catch (err: any) {
+      error.value = err.response?.data?.error?.message || err.response?.data?.detail || '删除代理节点失败'
+      throw err
+    } finally {
+      loading.value = false
+    }
+  }
+
+  return {
+    nodes,
+    total,
+    loading,
+    error,
+    fetchNodes,
+    deleteNode,
+  }
+})