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/tests/test_history_store_transactional.py

@@ -0,0 +1,141 @@
+"""ConversationHistoryStore transactional boundaries."""
+
+from __future__ import annotations
+
+from contextlib import asynccontextmanager
+from datetime import datetime, timezone
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.features.conversation.history_store import ConversationHistoryStore
+
+
+@asynccontextmanager
+async def _capture_transactional(db):
+    yield db
+    await db.commit()
+
+
+@pytest.mark.asyncio
+async def test_record_ai_only_turn_commits_before_redis_sync() -> None:
+    db = MagicMock(spec=AsyncSession)
+    db.commit = AsyncMock()
+    redis_sync = AsyncMock()
+    captured: list[object] = []
+
+    class FakeMsg:
+        def __init__(self, **kwargs) -> None:
+            self.id = "ai-1"
+            for k, v in kwargs.items():
+                setattr(self, k, v)
+
+    class _FakeRepo:
+        @staticmethod
+        def add_conversation_message(msg: object, _db) -> None:
+            captured.append(msg)
+
+    with patch(
+        "app.features.conversation.history_store.transactional",
+        _capture_transactional,
+    ), patch(
+        "app.features.conversation.history_store.ConversationMessage",
+        FakeMsg,
+    ), patch(
+        "app.features.conversation.history_store.repo",
+        _FakeRepo,
+    ):
+        store = ConversationHistoryStore(db)
+        store._sync_redis_best_effort = redis_sync  # type: ignore[method-assign]
+        store._touch_conversation = AsyncMock()  # type: ignore[method-assign]
+
+        msg_id = await store.record_ai_only_turn("conv-1", ["hello"])
+
+    assert msg_id is not None
+    assert len(captured) == 1
+    assert captured[0].id == msg_id
+    db.commit.assert_awaited_once()
+    redis_sync.assert_awaited_once_with("conv-1")
+
+
+@pytest.mark.asyncio
+async def test_attach_ai_tts_commits_repo_update_before_redis_sync() -> None:
+    db = MagicMock(spec=AsyncSession)
+    db.commit = AsyncMock()
+    redis_sync = AsyncMock()
+    repo_calls: list[tuple] = []
+
+    async def fake_set_latest(*args, **kwargs):
+        repo_calls.append((args, kwargs))
+        return object()
+
+    with patch(
+        "app.features.conversation.history_store.transactional",
+        _capture_transactional,
+    ), patch(
+        "app.features.conversation.history_store.repo.set_latest_ai_message_tts_audio_urls",
+        fake_set_latest,
+    ):
+        store = ConversationHistoryStore(db)
+        store._sync_redis_best_effort = redis_sync  # type: ignore[method-assign]
+
+        await store.attach_ai_tts_audio_urls(
+            "conv-1",
+            tts_audio_urls=["https://example.com/a.mp3"],
+            segment_id="seg-1",
+        )
+
+    assert len(repo_calls) == 1
+    db.commit.assert_awaited_once()
+    redis_sync.assert_awaited_once_with("conv-1")
+
+
+@pytest.mark.asyncio
+async def test_record_human_ai_turn_commits_pair_before_redis_sync() -> None:
+    db = MagicMock(spec=AsyncSession)
+    db.commit = AsyncMock()
+    redis_sync = AsyncMock()
+    captured: list[object] = []
+
+    class FakeMsg:
+        def __init__(self, **kwargs) -> None:
+            self.id = kwargs.get("id") or f"msg-{len(captured)}"
+            for k, v in kwargs.items():
+                setattr(self, k, v)
+
+    class _FakeRepo:
+        @staticmethod
+        def add_conversation_message(msg: object, _db) -> None:
+            captured.append(msg)
+
+    with patch(
+        "app.features.conversation.history_store.transactional",
+        _capture_transactional,
+    ), patch(
+        "app.features.conversation.history_store.ConversationMessage",
+        FakeMsg,
+    ), patch(
+        "app.features.conversation.history_store.repo",
+        _FakeRepo,
+    ):
+        store = ConversationHistoryStore(db)
+        store._sync_redis_best_effort = redis_sync  # type: ignore[method-assign]
+        store._touch_conversation = AsyncMock()  # type: ignore[method-assign]
+
+        out = await store.record_human_ai_turn(
+            "conv-1",
+            "hello",
+            ["reply"],
+            user_message_timestamp=datetime.now(timezone.utc),
+            is_from_voice=False,
+            voice_session_id=None,
+            audio_duration_seconds=None,
+            tts_audio_urls=None,
+            segment_id="seg-1",
+        )
+
+    assert out is not None
+    assert len(captured) == 2
+    db.commit.assert_awaited_once()
+    redis_sync.assert_awaited_once_with("conv-1")