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

tests/test_derived.py

@@ -0,0 +1,80 @@
+"""派生索引维护测试。"""
+
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from sqlalchemy import text
+
+from app.services.derived import reindex_chroma, reindex_fts
+
+
+class TestReindexFts:
+    def test_reindex_fts_rebuilds_missing_rows(self, db_session, sample_paper):
+        db_session.execute(
+            text("DELETE FROM papers_fts WHERE rowid = :id"),
+            {"id": sample_paper.id},
+        )
+        db_session.commit()
+
+        result = reindex_fts(db_session)
+
+        row = db_session.execute(
+            text("SELECT title_en, authors, tags FROM papers_fts WHERE rowid = :id"),
+            {"id": sample_paper.id},
+        ).fetchone()
+        assert result == {"status": "success", "indexed": 1}
+        assert row is not None
+        assert row[0] == sample_paper.title_en
+        assert "Alice Smith" in row[1]
+        assert "NLP" in row[2]
+
+    def test_reindex_fts_accepts_subset(self, db_session, sample_papers_range):
+        keep_id = sample_papers_range[0].id
+        skip_id = sample_papers_range[1].id
+        db_session.execute(text("DELETE FROM papers_fts"))
+        db_session.commit()
+
+        result = reindex_fts(db_session, paper_ids=[keep_id])
+
+        keep_row = db_session.execute(
+            text("SELECT rowid FROM papers_fts WHERE rowid = :id"),
+            {"id": keep_id},
+        ).fetchone()
+        skip_row = db_session.execute(
+            text("SELECT rowid FROM papers_fts WHERE rowid = :id"),
+            {"id": skip_id},
+        ).fetchone()
+        assert result["indexed"] == 1
+        assert keep_row is not None
+        assert skip_row is None
+
+
+class TestReindexChroma:
+    def test_reindex_chroma_indexes_only_summarized_papers(
+        self, db_session, sample_papers_with_summary
+    ):
+        with patch("app.services.embedder.index_paper", return_value=True) as mock_index:
+            result = reindex_chroma(db_session)
+
+        assert result["status"] == "success"
+        assert result["indexed"] == 4
+        assert mock_index.call_count == 4
+        indexed_ids = {call.args[0] for call in mock_index.call_args_list}
+        assert "2401.20001" in indexed_ids
+        assert "2401.20005" not in indexed_ids
+
+    def test_reindex_chroma_reports_partial_failures(
+        self, db_session, sample_papers_with_summary
+    ):
+        def _index_paper(arxiv_id, _texts):
+            if arxiv_id == "2401.20001":
+                raise RuntimeError("embedding failed")
+            return True
+
+        with patch("app.services.embedder.index_paper", side_effect=_index_paper):
+            result = reindex_chroma(db_session)
+
+        assert result["status"] == "partial"
+        assert result["indexed"] == 3
+        assert result["errors"] == ["2401.20001: embedding failed"]