refactor: extract admin business logic to services, introduce job queue, add derived index helpers

- Move DB operations from routes/admin.py to services/admin.py (get_logs_context, query_summary_statuses, retry_failed, delete/reset operations)
- Add services/jobs.py with Job/JobEvent-based async job queue (create_job, run_job, enqueue_job)
- Add services/derived.py with FTS5 reindex and paper index deletion helpers
- Refactor scheduler to use job queue instead of direct pipeline calls
- Add heartbeat_at/expires_at to TaskLock for lock health tracking
- Remove DESIGN_REVIEW.md
- Update tests: remove redundant integration tests, add unit tests for new services

app/services/summary_persister.py

@@ -3,8 +3,6 @@
 from __future__ import annotations
 
 import logging
-
-from sqlalchemy import text
 from sqlalchemy.orm import Session
 
 from app.models import (
@@ -13,6 +11,7 @@ from app.models import (
     PaperTag,
     SummaryState,
 )
+from app.services.derived import reindex_paper_fts
 from app.services.pdf_downloader import paper_dir
 from app.services.schemas import (
     SummarySchema,
@@ -75,19 +74,9 @@ def _update_summary_in_db(
             db.add(PaperTag(paper_id=paper.id, tag=tag_name, source="ai"))
             existing_tag_names.add(tag_name)
 
-    # 4. FTS5 更新
-    summary_text = _build_fts_summary_text(schema)
-    db.execute(
-        text(
-            "UPDATE papers_fts SET title_zh=:title_zh, summary_text=:summary_text "
-            "WHERE rowid=:paper_id"
-        ),
-        {
-            "title_zh": schema.title_zh,
-            "summary_text": summary_text,
-            "paper_id": paper.id,
-        },
-    )
+    # 4. FTS5 派生索引
+    db.flush()
+    reindex_paper_fts(db, paper)
 
     db.commit()
     logger.info("DB updated: paper=%s quality=%s", paper.arxiv_id, quality)