M2b：删除旧 chat 体系——线性会话/叩心/情绪/纪念日模型与页面退役（迁移 003 双向验证），runs 去会话外键，测试全量修剪

backend/app/services/serializers.py

@@ -6,7 +6,6 @@ from typing import Any
 from app.core.time import to_iso, utc_now
 from app.models.candidates import MemoryCandidate, ProfileCandidate
 from app.models.character import Character
-from app.models.chat import ChatMessage, ChatSession
 from app.models.governance import (
     AgentRosterEntry,
     GenerationPreferences,
@@ -33,7 +32,6 @@ from app.schemas.admin import (
 )
 from app.schemas.candidates import MemoryCandidateResponse, ProfileCandidateResponse
 from app.schemas.character import CharacterResponse, CharacterSummaryResponse
-from app.schemas.chat import ChatMessageResponse, ChatSessionResponse
 from app.schemas.imports import ImportItemResponse, ImportJobResponse
 from app.schemas.memory import MemoryResponse
 from app.schemas.personality import PersonalityProposalResponse, PersonalityResponse
@@ -125,42 +123,6 @@ def proposal_to_response(proposal: PersonalityProposal) -> PersonalityProposalRe
     )
 
 
-def chat_session_to_response(
-    chat_session: ChatSession,
-    *,
-    message_count: int = 0,
-    last_message_preview: str | None = None,
-) -> ChatSessionResponse:
-    return ChatSessionResponse(
-        session_id=chat_session.id,
-        character_id=chat_session.character_id,
-        title=chat_session.title,
-        status=chat_session.status,
-        created_at=to_iso(chat_session.created_at) or "",
-        updated_at=to_iso(chat_session.updated_at) or "",
-        message_count=message_count,
-        last_message_preview=last_message_preview,
-    )
-
-
-def chat_message_to_response(message: ChatMessage) -> ChatMessageResponse:
-    return ChatMessageResponse(
-        message_id=message.id,
-        session_id=message.session_id,
-        character_id=message.character_id,
-        role=message.role,
-        content=message.content,
-        modality=message.modality,
-        run_id=message.run_id,
-        metadata=loads_dict(message.metadata_json),
-        sensitivity=message.sensitivity,
-        versions=loads_list(message.versions_json),
-        active_version_idx=message.active_version_idx,
-        created_at=to_iso(message.created_at) or "",
-        deleted_at=to_iso(message.deleted_at),
-    )
-
-
 def memory_to_response(memory: Memory) -> MemoryResponse:
     return MemoryResponse(
         id=memory.id,
@@ -185,7 +147,6 @@ def run_to_response(run: Run) -> RunResponse:
     return RunResponse(
         id=run.id,
         character_id=run.character_id,
-        session_id=run.session_id,
         status=run.status,
         kind=run.kind,
         goal=run.goal,