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/tasks/memoir_quality_pass_tasks.py

@@ -17,13 +17,15 @@ from sqlalchemy.orm import Session
 
 from app.agents.memoir.narrative_agent import NarrativeAgent
 from app.core.config import settings
-from app.core.db import get_sync_db
+from app.core.db import get_sync_db, transactional_sync
 from app.core.llm_gateway import LlmGateway, LlmUseCase
 from app.core.logging import get_logger
 from app.core.memoir_pipeline_progress import merge_pipeline_run
 from app.features.memoir.models import Chapter
 from app.features.memoir.repo import mark_chapter_dirty_sync
 from app.features.story.models import Story
+from app.features.memoir.constants import memoir
+from app.features.story.constants import story
 
 logger = get_logger(__name__)
 
@@ -54,7 +56,7 @@ def _polish_story_title(
         return False
 
     body = (story.canonical_markdown or "").strip()
-    if len(body) < settings.story_title_min_body_chars:
+    if len(body) < story.title_min_body_chars:
         return False
 
     narrative_agent = NarrativeAgent()
@@ -76,7 +78,7 @@ def _polish_story_title(
     return True
 
 
-@shared_task(bind=True, max_retries=2, default_retry_delay=30)
+@shared_task(bind=True, max_retries=2, default_retry_delay=30, ignore_result=True)
 def memoir_quality_pass(
     self,
     user_id: str,
@@ -89,7 +91,7 @@ def memoir_quality_pass(
     Runs asynchronously after the fast draft is committed and visible.
     """
     qptid = str(self.request.id)
-    if not settings.memoir_quality_pass_enabled:
+    if not memoir.quality_pass_enabled:
         if memoir_correlation_id:
             merge_pipeline_run(
                 memoir_correlation_id,
@@ -152,34 +154,32 @@ def memoir_quality_pass(
                 == "en"
                 else "zh"
             )
-            for sid in story_ids:
-                story = db.get(Story, sid)
-                if not story or story.user_id != user_id:
-                    continue
+            with transactional_sync(db):
+                for sid in story_ids:
+                    story = db.get(Story, sid)
+                    if not story or story.user_id != user_id:
+                        continue
 
-                chapter_category = story.stage or "summary"
-                if _polish_story_title(
-                    db,
-                    story,
-                    llm,
-                    chapter_category=chapter_category,
-                    language=user_language,
-                ):
-                    titles_polished += 1
-                    stmt = select(Chapter.id).where(
-                        Chapter.user_id == user_id,
-                        Chapter.category == chapter_category,
-                        Chapter.is_active == True,  # noqa: E712
-                    )
-                    ch_id = db.execute(stmt).scalar_one_or_none()
-                    if ch_id:
-                        chapters_dirtied.add(str(ch_id))
+                    chapter_category = story.stage or "summary"
+                    if _polish_story_title(
+                        db,
+                        story,
+                        llm,
+                        chapter_category=chapter_category,
+                        language=user_language,
+                    ):
+                        titles_polished += 1
+                        stmt = select(Chapter.id).where(
+                            Chapter.user_id == user_id,
+                            Chapter.category == chapter_category,
+                            Chapter.is_active == True,  # noqa: E712
+                        )
+                        ch_id = db.execute(stmt).scalar_one_or_none()
+                        if ch_id:
+                            chapters_dirtied.add(str(ch_id))
 
-            for ch_id in chapters_dirtied:
-                mark_chapter_dirty_sync(db, ch_id)
-
-            if titles_polished > 0:
-                db.commit()
+                for ch_id in chapters_dirtied:
+                    mark_chapter_dirty_sync(db, ch_id)
 
         elapsed = time.perf_counter() - t0
         duration_ms = elapsed * 1000