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/compaction_service.py

@@ -16,6 +16,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from app.core.config import settings
 from app.core.logging import get_logger
 from app.features.memory.models import MemoryChunk, MemorySource
+from app.features.memory.constants import memory
 from app.features.memory.repo import (
     create_curation_action,
     get_first_chunk_after_cursor,
@@ -227,7 +228,7 @@ async def run_memory_compaction(
         cand_sources = [str(x) for x in cand_sources]
     has_candidate_filter = "candidate_chunk_ids" in ctx or "candidate_source_ids" in ctx
 
-    max_chunks = settings.memory_compaction_max_chunks_per_run
+    max_chunks = memory.compaction_max_chunks_per_run
     incremental = await list_incremental_chunks_for_compaction(
         db,
         user_id=user_id,
@@ -248,7 +249,7 @@ async def run_memory_compaction(
                 cursor_ts,
                 cursor_id,
                 max_steps=max(
-                    settings.memory_compaction_max_chunks_per_run * 2,
+                    memory.compaction_max_chunks_per_run * 2,
                     500,
                 ),
             )
@@ -288,12 +289,12 @@ async def run_memory_compaction(
             "skipped_reason": "empty_incremental",
         }
 
-    sim_th = settings.memory_compaction_chunk_similarity_threshold
-    min_layers = settings.memory_compaction_min_layers_for_exclude
-    jaccard_min = settings.memory_compaction_text_jaccard_min
-    year_w = settings.memory_compaction_metadata_event_year_window
-    max_neighbors = settings.memory_compaction_max_neighbors_per_chunk
-    max_excludes = settings.memory_compaction_max_excludes_per_run
+    sim_th = memory.compaction_chunk_similarity_threshold
+    min_layers = memory.compaction_min_layers_for_exclude
+    jaccard_min = memory.compaction_text_jaccard_min
+    year_w = memory.compaction_metadata_event_year_window
+    max_neighbors = memory.compaction_max_neighbors_per_chunk
+    max_excludes = memory.compaction_max_excludes_per_run
 
     local_excluded: set[str] = set()
     excludes_done = 0