perf: add DB performance indexes and fix N+1 query in backtest listing

Add 10 indexes across prices, etf_prices, financials, valuations,
holdings, transactions, signals, portfolio_snapshots, and etfs tables.
Fix N+1 query in list_backtests by eager-loading backtest results
with joinedload.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/alembic/versions/add_performance_indexes.py

@@ -0,0 +1,49 @@
+"""add performance indexes
+
+Revision ID: b7c8d9e0f1a2
+Revises: 606a5011f84f
+Create Date: 2026-03-18 22:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'b7c8d9e0f1a2'
+down_revision: Union[str, None] = '606a5011f84f'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Tier 1: backtest/strategy performance
+    op.create_index('idx_prices_ticker_date', 'prices', ['ticker', sa.text('date DESC')])
+    op.create_index('idx_etf_prices_ticker_date', 'etf_prices', ['ticker', sa.text('date DESC')])
+    op.create_index('idx_financials_ticker_base_date', 'financials', ['ticker', sa.text('base_date DESC')])
+    op.create_index('idx_valuations_ticker_base_date', 'valuations', ['ticker', sa.text('base_date DESC')])
+
+    # Tier 2: portfolio queries
+    op.create_index('idx_holdings_portfolio_id', 'holdings', ['portfolio_id'])
+    op.create_index('idx_transactions_portfolio_id_executed_at', 'transactions', ['portfolio_id', sa.text('executed_at DESC')])
+    op.create_index('idx_signals_date_status', 'signals', [sa.text('date DESC'), 'status'])
+    op.create_index('idx_snapshots_portfolio_date', 'portfolio_snapshots', ['portfolio_id', sa.text('snapshot_date DESC')])
+
+    # Tier 3: ETF filters
+    op.create_index('idx_etf_asset_class', 'etfs', ['asset_class'])
+    op.create_index('idx_etf_price_date', 'etf_prices', [sa.text('date DESC')])
+
+
+def downgrade() -> None:
+    op.drop_index('idx_etf_price_date', table_name='etf_prices')
+    op.drop_index('idx_etf_asset_class', table_name='etfs')
+    op.drop_index('idx_snapshots_portfolio_date', table_name='portfolio_snapshots')
+    op.drop_index('idx_signals_date_status', table_name='signals')
+    op.drop_index('idx_transactions_portfolio_id_executed_at', table_name='transactions')
+    op.drop_index('idx_holdings_portfolio_id', table_name='holdings')
+    op.drop_index('idx_valuations_ticker_base_date', table_name='valuations')
+    op.drop_index('idx_financials_ticker_base_date', table_name='financials')
+    op.drop_index('idx_etf_prices_ticker_date', table_name='etf_prices')
+    op.drop_index('idx_prices_ticker_date', table_name='prices')

backend/app/api/backtest.py

@@ -4,7 +4,7 @@ Backtest API endpoints.
 from typing import List
 
 from fastapi import APIRouter, Depends, HTTPException
-from sqlalchemy.orm import Session
+from sqlalchemy.orm import Session, joinedload
 
 from app.core.database import get_db
 from app.api.deps import CurrentUser
@@ -62,6 +62,7 @@ async def list_backtests(
     """List all backtests for current user."""
     backtests = (
         db.query(Backtest)
+        .options(joinedload(Backtest.result))
         .filter(Backtest.user_id == current_user.id)
         .order_by(Backtest.created_at.desc())
         .all()