feat(eval): Playground GLM 评分落库并可恢复

在 conversations 表增加 playground_conversation_judge_json，流式/非流式对话评审结束后写入最近一次快照（整体分、逐轮分、对比文案、错误与基线文件名等）。新增只读 GET 供前端按会话拉取；评测台 Playground 切换会话时自动恢复，并提示基线是否和当时一致。

api/app/features/evaluation/session_catalog_service.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
+from typing import Any
 
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -110,3 +111,12 @@ class SessionCatalogService:
             user_utterances_from_segments=from_segments,
             user_utterances_from_messages=from_messages,
         )
+
+    async def get_playground_conversation_judge_json(
+        self, conversation_id: str
+    ) -> dict[str, Any] | None:
+        c = await self._repo.get_conversation(conversation_id)
+        if not c or c.deleted_at:
+            return None
+        raw = c.playground_conversation_judge_json
+        return raw if isinstance(raw, dict) else None