feat: add portfolio optimization and congress tracking (TDD)

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

routes_regulators.py

@@ -1,10 +1,11 @@
-"""Routes for regulatory data (CFTC, SEC)."""
+"""Routes for regulatory data (CFTC, SEC, Congress)."""
 
 from fastapi import APIRouter, Path, Query
 
 from models import ApiResponse
 from route_utils import safe, validate_symbol
 import regulators_service
+import congress_service
 
 router = APIRouter(prefix="/api/v1/regulators")
 
@@ -49,3 +50,22 @@ async def sec_cik_map(symbol: str = Path(..., min_length=1, max_length=20)):
     symbol = validate_symbol(symbol)
     data = await regulators_service.get_cik_map(symbol)
     return ApiResponse(data=data)
+
+
+# --- Congress Trading ---
+
+
+@router.get("/congress/trades", response_model=ApiResponse)
+@safe
+async def congress_trades():
+    """Recent US congress member stock trades."""
+    data = await congress_service.get_congress_trades()
+    return ApiResponse(data=data)
+
+
+@router.get("/congress/bills", response_model=ApiResponse)
+@safe
+async def congress_bills(query: str = Query(..., min_length=1, max_length=200)):
+    """Search US congress bills by keyword."""
+    data = await congress_service.search_congress_bills(query)
+    return ApiResponse(data=data)