feat(api): 统一 LLM JSON 调用层 llm_json_call，按域 Schema 迁移 chat/memoir agents

api/app/agents/chat/schemas.py

@@ -0,0 +1,19 @@
+"""LLM JSON 边界契约（Chat agents）。"""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field
+
+
+class StageDetectionOutput(BaseModel):
+    detected_stage: str = Field(default="", description="CHAT_STAGES key")
+
+
+class ProfileExtractionOutput(BaseModel):
+    birth_year: int | str | None = None
+    birth_place: str | None = None
+    grew_up_place: str | None = None
+    occupation: str | None = None
+
+
+__all__ = ["ProfileExtractionOutput", "StageDetectionOutput"]