fix(vertex): SA 认证注入代理配置，细化 token 获取异常处理

- _auth_service_account 接收 endpoint 参数，通过 _get_proxy_config 解析代理
- vertex_auth 区分 TimeoutException/RequestError/通用异常，提供可读错误信息
- 新增测试覆盖代理传递和超时场景

src/core/vertex_auth.py

@@ -174,8 +174,16 @@ class VertexAuthService:
             raise VertexAuthError(
                 f"Failed to get access token: HTTP {e.response.status_code}: {error_body}"
             )
+        except httpx.TimeoutException:
+            raw = client_kwargs.get("timeout")
+            suffix = f" after {raw}s" if isinstance(raw, (int, float)) else ""
+            raise VertexAuthError(f"Failed to get access token: request timed out{suffix}")
+        except httpx.RequestError as e:
+            detail = str(e).strip() or type(e).__name__
+            raise VertexAuthError(f"Failed to get access token: {detail}")
         except Exception as e:
-            raise VertexAuthError(f"Failed to get access token: {e}")
+            detail = str(e).strip() or type(e).__name__
+            raise VertexAuthError(f"Failed to get access token: {detail}")
 
     @classmethod
     def clear_cache(cls, client_email: str | None = None) -> None:

src/services/provider/adapters/vertex_ai/auth.py

@@ -12,7 +12,7 @@ from typing import Any
 from src.core.provider_auth_types import ProviderAuthInfo
 
 
-async def _auth_service_account(key: Any) -> ProviderAuthInfo:
+async def _auth_service_account(key: Any, endpoint: Any | None = None) -> ProviderAuthInfo:
     """Service Account 认证：SA JSON → JWT → Access Token。"""
     from src.core.crypto import crypto_service
     from src.core.exceptions import InvalidRequestException
@@ -38,11 +38,14 @@ async def _auth_service_account(key: Any) -> ProviderAuthInfo:
             raise InvalidRequestException("Service Account JSON 无效，请重新添加该密钥。")
 
         # 获取 Access Token（注入代理配置）
+        from src.services.provider.auth import _get_proxy_config
         from src.services.proxy_node.resolver import build_proxy_client_kwargs
 
+        effective_proxy = _get_proxy_config(key, endpoint)
+
         service = VertexAuthService(sa_json)
         access_token = await service.get_access_token(
-            httpx_client_kwargs=build_proxy_client_kwargs(timeout=30),
+            httpx_client_kwargs=build_proxy_client_kwargs(effective_proxy, timeout=30),
         )
 
         return ProviderAuthInfo(

src/services/provider/auth.py

@@ -556,7 +556,7 @@ async def get_provider_auth(
         # "vertex_ai" 保留为向后兼容（迁移期间旧数据可能仍使用该值）
         from src.services.provider.adapters.vertex_ai.auth import _auth_service_account
 
-        return await _auth_service_account(key)
+        return await _auth_service_account(key, endpoint)
 
     # 标准 API Key：返回 None，由 build_headers 处理
     return None