- sec_filings_service: 루프 전 accession_number 일괄 pre-fetch로 N+1 제거
- sec_filings_service: 500건 단위 청크 커밋으로 all-or-nothing 트랜잭션 방지
- sec_filings_service: bulk 인덱싱 시 코루틴별 독립 세션 생성으로 동시 세션 충돌 해결
- sec_filings_service: index_filings 데드라인 60s → 120s, bulk timeout 동일 적용
- sec_http_client: _TokenBucket(10 req/sec) 추가로 SEC EDGAR 과부하 방지
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Extract shared SECHttpClient from ETF fetcher (retry, backoff, cache, throttle)
and apply it to both ETF and core SEC services, fixing missing rate limiting.
Add SECFiling DB model, Pydantic schemas, SECFilingsService with auto-indexing,
and REST endpoints at /filings/search, /filings/documents, /filings/exhibit.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>