feat: 上游 Key 唯一化、分组导入跳过、账号导入平台识别&远端校验&base_url 注入

- 上游 Key 命名改为 {prefix}-{upstream.id}-{safe_group_name}-{group_id}
- 唯一约束 (upstream_id, group_id, managed_prefix) 加 managed_prefix 列
- 上游检测成功时同步 Key 状态，远端已删/分组已删自动清理
- 重复分组导入跳过，目标网站已存在同名分组返回 exists
- 账号导入平台自动识别（auto/manual 模式）
- 全选可导入 Key 按钮 + 目标分组自动匹配
- 导入幂等：已导入过的 Key 校验远端账号，不存在则重建
- 新增同步接口 POST /sync-imported-upstream-keys
- account_exists() 通过拉取账号列表判断，避免 404 误判
- credentials.base_url 注入来源上游地址，避免 401
- 前端导入弹窗自动同步+刷新按钮+并发/优先级设置
- 新增 12 个测试覆盖同步、幂等、远端删除、校验失败路径

backend/app/schemas/upstream.py

@@ -1,6 +1,6 @@
 from datetime import datetime
 from typing import Optional, Any
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 
 
 class AuthConfigBearer(BaseModel):
@@ -89,3 +89,38 @@ class TestResult(BaseModel):
     success: bool
     message: str
     detail: Optional[str] = None
+
+
+class GenerateKeysByGroupsRequest(BaseModel):
+    group_ids: list[str] = Field(default_factory=list)
+    name_prefix: str = "SmartUp"
+    quota: float = Field(default=0, ge=0)
+    expires_in_days: Optional[int] = Field(default=None, ge=1)
+    rate_limit_5h: float = Field(default=0, ge=0)
+    rate_limit_1d: float = Field(default=0, ge=0)
+    rate_limit_7d: float = Field(default=0, ge=0)
+    endpoint: str = "/keys"
+
+
+class GeneratedUpstreamKeyResponse(BaseModel):
+    id: Optional[int] = None
+    upstream_id: int
+    group_id: str
+    group_name: str = ""
+    key_id: Optional[str] = None
+    key_name: str
+    key_value: Optional[str] = None
+    masked_key: str = ""
+    status: str
+    error: Optional[str] = None
+    imported_website_id: Optional[int] = None
+    imported_account_id: Optional[str] = None
+    imported_at: Optional[datetime] = None
+    created_at: Optional[datetime] = None
+    updated_at: Optional[datetime] = None
+
+
+class GenerateKeysByGroupsResponse(BaseModel):
+    success: bool
+    message: str
+    items: list[GeneratedUpstreamKeyResponse]