Portfolio optimization (3 endpoints):
- POST /portfolio/optimize - HRP optimal weights via scipy clustering
- POST /portfolio/correlation - pairwise correlation matrix
- POST /portfolio/risk-parity - inverse-volatility risk parity weights
Congress tracking (2 endpoints):
- GET /regulators/congress/trades - congress member stock trades
- GET /regulators/congress/bills?query= - search congress bills
Implementation:
- portfolio_service.py: HRP with scipy fallback to inverse-vol
- congress_service.py: multi-provider fallback pattern
- 51 new tests (14 portfolio unit, 20 portfolio route, 12 congress
unit, 7 congress route)
- All 312 tests passing
