feat(universe): B1-1 指数历史成分（index_weight）+ Universe 按 as_of 成分过滤

- index_weight 表（migration f5e0d1c2b3a4，MySQL 已应用；index_code+date+symbol 唯一）
  + IndexWeight 实体 + IndexConstituentRepository（members_at：取 <=as_of 最近一期快照，
  Survivorship-free / 无未来成分；latest_date）
- UniverseSpec.index_code + universe.filter_stocks members 交集 + resolve_members；
  Research/Selection/Signal/Replay 服务注入 index repo（历史成分过滤，选股/回测共用）
- tests/test_index_universe.py：快照历史成分（成分变更不入早期结果）、幂等、
  空快照期空集、index_code 过滤下 as_of 一致性；全量 pytest 通过

backend/app/api/deps.py

@@ -16,6 +16,7 @@ from app.application.services.selection_service import SelectionService
 from app.application.services.signal_service import SignalService
 from app.domain.repositories.composite import CompositeRepository
 from app.domain.repositories.factor import FactorRepository
+from app.domain.repositories.index import IndexConstituentRepository
 from app.domain.repositories.jobs import ExperimentRepository, JobRepository
 from app.domain.repositories.market import (
     AdjustFactorRepository,
@@ -32,6 +33,9 @@ from app.infrastructure.persistence.sqlalchemy.repositories.composite_impl impor
 from app.infrastructure.persistence.sqlalchemy.repositories.factor_impl import (
     SqlAlchemyFactorRepository,
 )
+from app.infrastructure.persistence.sqlalchemy.repositories.index_impl import (
+    SqlAlchemyIndexConstituentRepository,
+)
 from app.infrastructure.persistence.sqlalchemy.repositories.market_impl import (
     SqlAlchemyAdjustFactorRepository,
     SqlAlchemyDailyBarRepository,
@@ -78,6 +82,10 @@ def _chart_service_factory(
     return ChartService(stock_repo, daily_repo, adj_repo)
 
 
+def _index_repo_factory(session: DbSession) -> IndexConstituentRepository:
+    return SqlAlchemyIndexConstituentRepository(session)
+
+
 def _engine_factory() -> QuantEngine:
     return LocalEngine()
 
@@ -86,31 +94,34 @@ def _service_factory(
     stock_repo: Annotated[StockRepository, Depends(_stock_repo_factory)],
     daily_repo: Annotated[DailyBarRepository, Depends(_daily_repo_factory)],
     engine: Annotated[QuantEngine, Depends(_engine_factory)],
+    index_repo: Annotated[IndexConstituentRepository, Depends(_index_repo_factory)],
 ) -> ResearchService:
-    return ResearchService(stock_repo, daily_repo, engine)
+    return ResearchService(stock_repo, daily_repo, engine, index_repo)
 
 
 def _replay_service_factory(
     stock_repo: Annotated[StockRepository, Depends(_stock_repo_factory)],
     daily_repo: Annotated[DailyBarRepository, Depends(_daily_repo_factory)],
+    index_repo: Annotated[IndexConstituentRepository, Depends(_index_repo_factory)],
 ) -> ReplayService:
-    return ReplayService(stock_repo, daily_repo)
+    return ReplayService(stock_repo, daily_repo, index_repo)
 
 
 def _signal_service_factory(
     stock_repo: Annotated[StockRepository, Depends(_stock_repo_factory)],
     daily_repo: Annotated[DailyBarRepository, Depends(_daily_repo_factory)],
+    index_repo: Annotated[IndexConstituentRepository, Depends(_index_repo_factory)],
 ) -> SignalService:
-    return SignalService(stock_repo, daily_repo)
+    return SignalService(stock_repo, daily_repo, index_repo)
 
 
 def _selection_service_factory(
     stock_repo: Annotated[StockRepository, Depends(_stock_repo_factory)],
     daily_repo: Annotated[DailyBarRepository, Depends(_daily_repo_factory)],
     financial_repo: Annotated[FinancialRepository, Depends(_financial_repo_factory)],
+    index_repo: Annotated[IndexConstituentRepository, Depends(_index_repo_factory)],
 ) -> SelectionService:
-    
-    return SelectionService(stock_repo, daily_repo, financial_repo)
+    return SelectionService(stock_repo, daily_repo, financial_repo, index_repo)
 
 
 def _selection_repo_factory(session: DbSession) -> SelectionRepository: