Initial implementation of Options Sidekick

Full-stack iOS options trading assistant:
- Python FastAPI backend with SQLite, APScheduler (15-min position monitor),
  APNs push notifications, and yfinance market data integration
- Signal engine: IV Rank (rolling HV proxy), SMA-50/200, swing-based
  support/resistance, earnings detection, signal strength scoring and
  noise-resistant SHA hash for change detection
- Recommendation engine: covered call and cash-secured put strike/expiry
  selection across 0DTE, 1DTE, weekly, and monthly horizons
- REST API: /devices, /portfolio, /recommendations, /positions, /signals, /alerts
- iOS SwiftUI app (iOS 17+): dashboard, recommendations, trades, portfolio,
  and alerts tabs with push notification deep-linking
- Unit + integration tests for signal engine and API layer

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

backend/app/database.py

@@ -0,0 +1,27 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker, DeclarativeBase
+from app.config import settings
+
+engine = create_engine(
+    settings.database_url,
+    connect_args={"check_same_thread": False} if "sqlite" in settings.database_url else {},
+)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+def init_db():
+    from app.models.db_models import Device, StockPosition, OptionPosition, Recommendation, Alert  # noqa: F401
+    Base.metadata.create_all(bind=engine)