refactor(api): TOML 配置 SSOT、统一错误契约、Auth/事务加固与可观测性 (#33)

配置 SSOT（TOML + .env）
统一错误契约
Auth 与事务边界
Redis / Celery 可靠性:业务 Redis（DB/0）与 Celery broker/backend（DB/1）显式拆分；连接池、sync client
可观测性（OpenTelemetry + LGTM）

api/app/features/conversation/ws/router.py

@@ -12,13 +12,11 @@ from starlette.websockets import WebSocketState
 
 from app.agents.chat.background_voice import infer_background_voice
 from app.agents.chat.prompts_profile import format_user_profile_context
-from app.agents.stage_constants import STAGE_TO_ORDER
 from app.core.config import settings
 from app.core.db import AsyncSessionLocal
 from app.core.dependencies import get_asr_provider
 from app.core.logging import get_logger
 from app.core.security import verify_token
-from app.features.conversation.history_store import ConversationHistoryStore
 from app.features.conversation.service import ConversationService
 from app.features.conversation.ws.connection_manager import manager
 from app.features.conversation.ws.message_types import MessageType
@@ -30,7 +28,6 @@ from app.features.conversation.ws.pipeline import (
     cleanup_segment_states,
     get_or_create_segment_state,
     handle_tts_request_on_demand,
-    memoir_ingest_scheduler,
     process_audio_segment,
     process_conversation_segments,
     process_persisted_user_segment_response,
@@ -40,9 +37,10 @@ from app.features.conversation.ws.pipeline import (
 from app.features.conversation.ws.profile_collector import get_missing_profile_fields
 from app.features.conversation.ws.quota_guard import check_ws_quota
 from app.features.conversation.ws.topic_chips_push import maybe_send_topic_chips_ws
-from app.features.memoir.state_service import get_or_create_state
+from app.features.memoir.service import MemoirService
 from app.features.quota.service import QuotaService
-from app.features.user.models import User
+from app.features.user.service import UserService
+from app.features.conversation.constants import chat
 
 logger = get_logger(__name__)
 
@@ -92,7 +90,8 @@ async def websocket_endpoint(
         return
 
     async with AsyncSessionLocal() as db:
-        user = await db.get(User, user_id)
+        user_service = UserService(db)
+        user = await user_service.get_by_id(user_id)
         if not user:
             await websocket.close(
                 code=status.WS_1008_POLICY_VIOLATION, reason="用户不存在"
@@ -108,6 +107,7 @@ async def websocket_endpoint(
 
         quota_service = QuotaService(db=db)
         conversation_service = ConversationService(db=db, quota_service=quota_service)
+        memoir_service = MemoirService(db=db)
 
         try:
             await manager.send_message(
@@ -158,15 +158,10 @@ async def websocket_endpoint(
 
             # 冷启动对齐 conversation_stage 与 MemoirState.current_stage；
             # 若对话行已有更靠前的人生阶段（STAGE_TO_ORDER 更大），不覆盖以免回退。
-            memoir_state = await get_or_create_state(user_id, db)
-            ms = (memoir_state.current_stage or "").strip()
-            cs = (conversation.conversation_stage or "").strip()
-            if ms:
-                if not cs:
-                    conversation.conversation_stage = ms
-                elif STAGE_TO_ORDER.get(ms, -1) >= STAGE_TO_ORDER.get(cs, -1):
-                    conversation.conversation_stage = ms
-            await db.commit()
+            memoir_state = await memoir_service.get_or_create_memoir_state(user_id)
+            await conversation_service.align_conversation_stage_from_memoir(
+                conversation, memoir_state.current_stage or ""
+            )
             await db.refresh(conversation)
 
             history = await conversation_service.ensure_redis_history_from_db(
@@ -184,7 +179,7 @@ async def websocket_endpoint(
                 """统一：把一组 AI 消息落库并按 [SPLIT] 分段下发。"""
                 if not texts:
                     return
-                ai_msg_id = await ConversationHistoryStore(db).record_ai_only_turn(
+                ai_msg_id = await conversation_service.record_ai_only_turn(
                     conversation_id, texts
                 )
                 if not ai_msg_id:
@@ -271,9 +266,9 @@ async def websocket_endpoint(
             else:
                 # 历史非空：判断是否需要回访问候（距上次消息超过阈值）
                 idle_hours = _idle_hours_since(conversation.last_message_at)
-                threshold = float(settings.chat_re_greeting_idle_hours)
+                threshold = float(chat.re_greeting_idle_hours)
                 if (
-                    settings.chat_re_greeting_enabled
+                    chat.re_greeting_enabled
                     and not get_missing_profile_fields(user)
                     and idle_hours is not None
                     and idle_hours >= threshold
@@ -383,11 +378,6 @@ async def websocket_endpoint(
                                 user_id,
                                 text_message,
                             )
-                            await memoir_ingest_scheduler.queue_segment(
-                                conversation.user_id,
-                                segment.id,
-                                text_char_count=len(text_message.strip()),
-                            )
 
                             task = asyncio.create_task(
                                 process_persisted_user_segment_response(
@@ -645,11 +635,6 @@ async def websocket_endpoint(
                                         audio_duration_seconds=ads if ads > 0 else None,
                                     )
                                 )
-                                await memoir_ingest_scheduler.queue_segment(
-                                    conversation.user_id,
-                                    segment.id,
-                                    text_char_count=len((asr_text or "").strip()),
-                                )
 
                                 if asr_text and not asr_text.startswith("转写失败"):
                                     task = asyncio.create_task(