fix: 修复proxy_service和account_service中不当的顶层import

- proxy_service.py: 将requests和WhitelistManager改为函数内延迟import，
  避免启动时加载不需要的依赖；移除未使用的get_exit_ip_via_proxy导入
- account_service.py: 移除未使用的func、joinedload、AuditLog、
  user_has_permission顶层导入

core/douyu/proxy_verifier.py

@@ -0,0 +1,114 @@
+"""代理可用性验证。"""
+
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from typing import Optional
+import time as _time
+
+import requests
+from loguru import logger
+
+
+def verify_proxy_url(proxy_url: str, timeout: tuple = (5, 8)) -> tuple[bool, str]:
+    """
+    验证代理是否可用，只验证斗鱼主站（登录的最终目标）。
+
+    Returns:
+        (是否可用, 消息)
+    """
+    from utils.http_logger import log_http
+
+    proxies = {'http': proxy_url, 'https': proxy_url}
+    started = _time.monotonic()
+    try:
+        response = requests.get(
+            'https://www.douyu.com',
+            proxies=proxies,
+            timeout=timeout,
+            headers={'User-Agent': 'Mozilla/5.0'},
+        )
+        elapsed = _time.monotonic() - started
+        response.raise_for_status()
+        log_http(
+            category="proxy_verify", method="GET", url="https://www.douyu.com",
+            status_code=response.status_code, response_body=f"代理可用: {proxy_url}",
+            duration=elapsed, proxy=proxy_url, tag="proxy_verify",
+        )
+        return True, '代理可用 → 斗鱼主站'
+    except Exception as exc:
+        elapsed = _time.monotonic() - started
+        err_msg = str(exc)
+        if 'Tunnel connection failed' in err_msg or '503' in err_msg:
+            detail = '代理拒绝连接（白名单可能未生效）'
+        elif 'timed out' in err_msg.lower():
+            detail = '连接超时'
+        else:
+            detail = type(exc).__name__
+        logger.debug(f"代理验证失败 [{proxy_url}]: {detail}")
+        log_http(
+            category="proxy_verify", method="GET", url="https://www.douyu.com",
+            duration=elapsed, error=f"[{proxy_url}] {detail}: {err_msg[:200]}",
+            proxy=proxy_url, tag="proxy_verify",
+        )
+        return False, detail
+
+
+def verify_proxies_concurrent(
+    proxy_urls: list[str],
+    timeout: tuple = (5, 8),
+    max_workers: int = 5,
+    return_all: bool = False,
+) -> tuple[Optional[str | list[str]], str]:
+    """
+    并发验证多个代理 URL。
+
+    Returns:
+        return_all=False: (可用代理 URL 或 None, 消息)
+        return_all=True: (可用代理 URL 列表或 None, 消息)
+    """
+    if not proxy_urls:
+        return None, '无代理可验证'
+
+    if len(proxy_urls) == 1:
+        ok, msg = verify_proxy_url(proxy_urls[0], timeout)
+        if ok:
+            return (proxy_urls if return_all else proxy_urls[0]), msg
+        return None, msg
+
+    if return_all:
+        available: list[str] = []
+        with ThreadPoolExecutor(max_workers=min(max_workers, len(proxy_urls))) as executor:
+            future_map = {
+                executor.submit(verify_proxy_url, proxy, timeout): proxy
+                for proxy in proxy_urls
+            }
+            for future in as_completed(future_map):
+                try:
+                    ok, _ = future.result()
+                    if ok:
+                        available.append(future_map[future])
+                except Exception:
+                    continue
+        if available:
+            logger.success(f"并发验证找到 {len(available)}/{len(proxy_urls)} 个可用代理")
+            return available, f'找到 {len(available)} 个可用代理'
+        return None, f'共 {len(proxy_urls)} 个代理均不可用'
+
+    with ThreadPoolExecutor(max_workers=min(max_workers, len(proxy_urls))) as executor:
+        future_map = {
+            executor.submit(verify_proxy_url, proxy, timeout): proxy
+            for proxy in proxy_urls
+        }
+        for future in as_completed(future_map):
+            proxy_url = future_map[future]
+            try:
+                ok, msg = future.result()
+                if ok:
+                    logger.success(f"并发验证找到可用代理: {proxy_url}")
+                    for item in future_map:
+                        if item != future:
+                            item.cancel()
+                    return proxy_url, msg
+            except Exception:
+                continue
+
+    return None, f'共 {len(proxy_urls)} 个代理均不可用'