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/memory/service.py

@@ -7,6 +7,7 @@ Celery task 只能作为同步入口包装 async service，不再维护 sync mem
 
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.core.db import transactional
 from app.core.logging import get_logger
 from app.features.memory.embedding_service import MemoryEmbeddingService
 from app.features.memory.ingest_service import MemoryIngestService
@@ -57,7 +58,7 @@ class MemoryService:
     async def ingest_transcripts_batch(
         self,
         user_id: str,
-        items: list[tuple[str, str, dict | None]],
+        items: list[tuple[str, str, dict | None, str | None]],
         *,
         memoir_correlation_id: str | None = None,
     ) -> list[str]:
@@ -112,71 +113,71 @@ class MemoryService:
     async def exclude_chunk(
         self, user_id: str, chunk_id: str, *, reason: str = ""
     ) -> bool:
-        ok = await set_chunk_excluded(self._db, chunk_id, user_id, True)
-        if not ok:
-            return False
-        stale_count = await mark_facts_stale_for_excluded_chunk(
-            self._db,
-            user_id=user_id,
-            chunk_id=chunk_id,
-        )
-        await create_curation_action(
-            self._db,
-            user_id=user_id,
-            action_type="exclude",
-            target_type="chunk",
-            target_id=chunk_id,
-            details={
-                **({"reason": reason} if reason else {}),
-                "staled_fact_count": stale_count,
-            },
-        )
-        await self._db.commit()
+        async with transactional(self._db):
+            ok = await set_chunk_excluded(self._db, chunk_id, user_id, True)
+            if not ok:
+                return False
+            stale_count = await mark_facts_stale_for_excluded_chunk(
+                self._db,
+                user_id=user_id,
+                chunk_id=chunk_id,
+            )
+            await create_curation_action(
+                self._db,
+                user_id=user_id,
+                action_type="exclude",
+                target_type="chunk",
+                target_id=chunk_id,
+                details={
+                    **({"reason": reason} if reason else {}),
+                    "staled_fact_count": stale_count,
+                },
+            )
         return True
 
     async def restore_chunk(self, user_id: str, chunk_id: str) -> bool:
-        ok = await set_chunk_excluded(self._db, chunk_id, user_id, False)
-        if not ok:
-            return False
-        await create_curation_action(
-            self._db,
-            user_id=user_id,
-            action_type="restore",
-            target_type="chunk",
-            target_id=chunk_id,
-            details={"fact_restore_policy": "requires_reenrichment"},
-        )
-        await self._db.commit()
+        async with transactional(self._db):
+            ok = await set_chunk_excluded(self._db, chunk_id, user_id, False)
+            if not ok:
+                return False
+            await create_curation_action(
+                self._db,
+                user_id=user_id,
+                action_type="restore",
+                target_type="chunk",
+                target_id=chunk_id,
+                details={"fact_restore_policy": "requires_reenrichment"},
+            )
         return True
 
     async def confirm_fact(self, user_id: str, fact_id: str) -> bool:
-        ok = await set_memory_fact_status(self._db, fact_id, user_id, "confirmed")
-        if not ok:
-            return False
-        await create_curation_action(
-            self._db,
-            user_id=user_id,
-            action_type="confirm",
-            target_type="fact",
-            target_id=fact_id,
-            details=None,
-        )
-        await self._db.commit()
+        async with transactional(self._db):
+            ok = await set_memory_fact_status(self._db, fact_id, user_id, "confirmed")
+            if not ok:
+                return False
+            await create_curation_action(
+                self._db,
+                user_id=user_id,
+                action_type="confirm",
+                target_type="fact",
+                target_id=fact_id,
+                details=None,
+            )
         return True
 
     async def reject_fact(
         self, user_id: str, fact_id: str, *, reason: str = ""
     ) -> bool:
-        ok = await set_memory_fact_status(self._db, fact_id, user_id, "rejected")
-        if not ok:
-            return False
-        await create_curation_action(
-            self._db,
-            user_id=user_id,
-            action_type="reject",
-            target_type="fact",
-            target_id=fact_id,
-            details={"reason": reason} if reason else None,
-        )
-        await self._db.commit()
-        return ok
+        async with transactional(self._db):
+            ok = await set_memory_fact_status(self._db, fact_id, user_id, "rejected")
+            if not ok:
+                return False
+            await create_curation_action(
+                self._db,
+                user_id=user_id,
+                action_type="reject",
+                target_type="fact",
+                target_id=fact_id,
+                details={"reason": reason} if reason else None,
+            )
+        return True