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/story/post_commit.py

@@ -6,37 +6,26 @@ enqueue 失败不回滚已提交数据，仅记录日志；依赖后续触发或
 
 from __future__ import annotations
 
-import threading
 from dataclasses import dataclass, field
 from datetime import datetime, timezone
 from typing import Any, cast
 
-import redis
-
-from app.core.config import settings
 from app.core.logging import get_logger
 from app.core.memoir_pipeline_progress import merge_pipeline_run
 from app.core.memory_compaction_schedule import schedule_memory_compaction_run
+from app.core.redis_sync import get_sync_redis
+from app.features.memoir.constants import memoir
+from app.features.story.constants import story
 
 logger = get_logger(__name__)
-_redis_client: redis.Redis | None = None
-_redis_lock = threading.Lock()
 
 
 def _story_image_enqueue_key(story_id: str) -> str:
     return f"enqueue:story-image:{story_id}"
 
 
-def _get_redis() -> redis.Redis:
-    """进程内复用单个 Redis 客户端，避免重复创建连接池。"""
-    global _redis_client
-    if _redis_client is None:
-        with _redis_lock:
-            if _redis_client is None:
-                _redis_client = redis.from_url(
-                    settings.redis_url, decode_responses=True
-                )
-    return _redis_client
+def _get_redis():
+    return get_sync_redis(decode_responses=True)
 
 
 @dataclass
@@ -68,7 +57,7 @@ def enqueue_story_post_commit_effects(
     """
     result = PostCommitResult()
     r = _get_redis()
-    ttl = int(settings.story_image_enqueue_dedup_ttl)
+    ttl = int(story.image_enqueue_dedup_ttl)
 
     if need_image and story_ids:
         from app.tasks.story_image_tasks import (
@@ -131,7 +120,7 @@ def enqueue_story_post_commit_effects(
             recompose_chapter as recompose_chapter_task,
         )
 
-        cd = int(settings.recompose_chapter_delay_seconds)
+        cd = int(story.recompose_chapter_delay_seconds)
         for cid in sorted(chapter_ids):
             try:
                 rkwargs: dict[str, Any] = {}
@@ -201,13 +190,13 @@ def enqueue_story_post_commit_effects(
             )
             result.errors.append(f"compaction:{exc}")
 
-    if need_quality_pass and settings.memoir_quality_pass_enabled and story_ids:
+    if need_quality_pass and memoir.quality_pass_enabled and story_ids:
         try:
             from app.tasks.memoir_quality_pass_tasks import (
                 memoir_quality_pass as quality_pass_task,
             )
 
-            cd = int(settings.memoir_quality_pass_delay_seconds)
+            cd = int(memoir.quality_pass_delay_seconds)
             qp_ar = cast(Any, quality_pass_task).apply_async(
                 args=[user_id, sorted(story_ids), sorted(chapter_ids)],
                 kwargs={"memoir_correlation_id": memoir_correlation_id},