feat(pool,priority): 号池聚合显示、API 格式归一化与优先级管理重构

- 优先级管理对话框按 family 分组显示 API 格式，号池 key 聚合为单条目展示
- 拖拽排序改用 key ID 替代数组索引，号池聚合项禁用拖拽/编辑/开关操作
- 后端 key 分组查询增加 API 格式键归一化，返回 provider_id
- 提取 OAuth auth_config 解密逻辑，新增 _derive_oauth_expires_at 从加密配置派生过期时间
- 号池管理移除会话列，调整 OAuth 过期信息与刷新按钮的布局顺序

tests/unit/test_pool_oauth_expires.py

@@ -0,0 +1,40 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from types import SimpleNamespace
+
+from src.api.admin.pool import routes as pool_routes
+
+
+def test_derive_oauth_expires_at_from_auth_config_seconds(monkeypatch) -> None:
+    key = SimpleNamespace(auth_type="oauth", auth_config="enc", expires_at=None)
+
+    monkeypatch.setattr(
+        pool_routes.crypto_service,
+        "decrypt",
+        lambda _v: '{"expires_at": 1710000000}',
+    )
+
+    assert pool_routes._derive_oauth_expires_at(key) == 1710000000
+
+
+def test_derive_oauth_expires_at_from_auth_config_milliseconds(monkeypatch) -> None:
+    key = SimpleNamespace(auth_type="oauth", auth_config="enc", expires_at=None)
+
+    monkeypatch.setattr(
+        pool_routes.crypto_service,
+        "decrypt",
+        lambda _v: '{"expires_at": 1710000000000}',
+    )
+
+    assert pool_routes._derive_oauth_expires_at(key) == 1710000000
+
+
+def test_derive_oauth_expires_at_fallback_to_legacy_datetime() -> None:
+    key = SimpleNamespace(
+        auth_type="oauth",
+        auth_config=None,
+        expires_at=datetime(2026, 3, 4, 1, 2, 3, tzinfo=timezone.utc),
+    )
+
+    assert pool_routes._derive_oauth_expires_at(key) == 1772586123