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。

src/services/proxy_node/__init__.py

@@ -0,0 +1,5 @@
+"""Proxy node services."""
+
+from .health_scheduler import ProxyNodeHealthScheduler, get_proxy_node_health_scheduler
+
+__all__ = ["ProxyNodeHealthScheduler", "get_proxy_node_health_scheduler"]

src/services/proxy_node/health_scheduler.py

@@ -0,0 +1,103 @@
+"""
+ProxyNode 心跳检测调度器
+
+定期检查 proxy_nodes 的 last_heartbeat_at，更新节点状态：
+- elapsed > interval * 3  -> unhealthy
+- elapsed > interval * 10 -> offline
+"""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Any
+
+from src.core.logger import logger
+from src.database import create_session
+from src.models.database import ProxyNode, ProxyNodeStatus
+from src.services.system.scheduler import get_scheduler
+
+
+class ProxyNodeHealthScheduler:
+    """代理节点心跳检测调度器"""
+
+    def __init__(self) -> None:
+        self.running = False
+
+    async def start(self) -> Any:
+        if self.running:
+            logger.warning("ProxyNodeHealthScheduler already running")
+            return
+
+        self.running = True
+        logger.info("ProxyNodeHealthScheduler started")
+
+        scheduler = get_scheduler()
+        scheduler.add_interval_job(
+            self._scheduled_check,
+            seconds=30,
+            job_id="proxy_node_health_check",
+            name="代理节点心跳检测",
+        )
+
+        # 启动时立即执行一次
+        await self._check_heartbeats()
+
+    async def stop(self) -> Any:
+        if not self.running:
+            return
+        self.running = False
+        logger.info("ProxyNodeHealthScheduler stopped")
+
+    async def _scheduled_check(self) -> None:
+        await self._check_heartbeats()
+
+    async def _check_heartbeats(self) -> None:
+        db = create_session()
+        try:
+            now = datetime.now(timezone.utc)
+            nodes = db.query(ProxyNode).filter(ProxyNode.status != ProxyNodeStatus.OFFLINE).all()
+            if not nodes:
+                return
+
+            changed = 0
+            for node in nodes:
+                interval = int(node.heartbeat_interval or 30)
+                last = node.last_heartbeat_at
+
+                if last is None:
+                    new_status = ProxyNodeStatus.OFFLINE
+                else:
+                    elapsed = (now - last).total_seconds()
+                    if elapsed > interval * 10:
+                        new_status = ProxyNodeStatus.OFFLINE
+                    elif elapsed > interval * 3:
+                        new_status = ProxyNodeStatus.UNHEALTHY
+                    else:
+                        new_status = ProxyNodeStatus.ONLINE
+
+                if node.status != new_status:
+                    node.status = new_status
+                    node.updated_at = now
+                    changed += 1
+
+            if changed:
+                db.commit()
+                logger.info("ProxyNode 心跳状态已更新: {} 个节点", changed)
+        except Exception as e:
+            try:
+                db.rollback()
+            except Exception:
+                pass
+            logger.exception("ProxyNode 心跳检测失败: {}", e)
+        finally:
+            db.close()
+
+
+_proxy_node_health_scheduler: ProxyNodeHealthScheduler | None = None
+
+
+def get_proxy_node_health_scheduler() -> ProxyNodeHealthScheduler:
+    global _proxy_node_health_scheduler
+    if _proxy_node_health_scheduler is None:
+        _proxy_node_health_scheduler = ProxyNodeHealthScheduler()
+    return _proxy_node_health_scheduler

src/services/task/service.py

@@ -704,6 +704,7 @@ class TaskService:
         from src.core.exceptions import (
             ConcurrencyLimitError,
             EmbeddedErrorException,
+            ProxyNodeUnavailableError,
             ThinkingSignatureException,
             UpstreamClientException,
         )
@@ -744,6 +745,20 @@ class TaskService:
             )
             return "break"
 
+        if isinstance(cause, ProxyNodeUnavailableError):
+            # ProxyNode 不可用属于“配置明确指定但不可达/不可用”的情况，
+            # 在当前候选上重试通常没有意义，直接切换到下一个候选更合理。
+            logger.warning("  [{}] 代理节点不可用，切换候选: {}", request_id, str(cause))
+            RequestCandidateService.mark_candidate_failed(
+                db=self.db,
+                candidate_id=candidate_record_id,
+                error_type=type(cause).__name__,
+                error_message=extract_error_message(cause),
+                latency_ms=elapsed_ms,
+                concurrent_requests=captured_key_concurrent,
+            )
+            return "break"
+
         if isinstance(cause, EmbeddedErrorException):
             error_message = cause.error_message or ""
             embedded_status = cause.error_code or 200