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/pipeline.py

@@ -7,6 +7,7 @@ from __future__ import annotations
 
 import logging
 from datetime import date as date_type
+from datetime import timedelta
 
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
@@ -32,6 +33,8 @@ def acquire_lock(db: Session, task: str, lock_key: str, owner: str) -> TaskLock:
         status="running",
         owner=owner,
         acquired_at=utc_now(),
+        heartbeat_at=utc_now(),
+        expires_at=utc_now() + timedelta(hours=6),
     )
     try:
         db.add(lock)
@@ -42,7 +45,12 @@ def acquire_lock(db: Session, task: str, lock_key: str, owner: str) -> TaskLock:
     return lock
 
 
-async def run_crawl(db: Session, target_date: str, owner: str = "admin_crawl") -> dict:
+async def run_crawl(
+    db: Session,
+    target_date: str,
+    owner: str = "admin_crawl",
+    top_n: int | None = None,
+) -> dict:
     """执行单次抓取（带防重入锁）。
 
     Args:
@@ -55,7 +63,7 @@ async def run_crawl(db: Session, target_date: str, owner: str = "admin_crawl") -
     """
     lock = acquire_lock(db, "crawl", target_date, owner)
     try:
-        return await crawl_daily(db, target_date)
+        return await crawl_daily(db, target_date, top_n=top_n)
     finally:
         release_lock(db, lock)
 
@@ -83,6 +91,8 @@ async def run_pipeline(db: Session, target_date: str, owner: str) -> dict:
         status="running",
         owner=owner,
         acquired_at=now,
+        heartbeat_at=now,
+        expires_at=now + timedelta(hours=6),
     )
     try:
         db.add(lock)