feat(stock-lab): /nodes + /settings 라우터 + main.py include

- screener/router.py: APIRouter prefix=/api/stock/screener
  - GET /nodes: NODE_REGISTRY + GATE_REGISTRY 메타 노출 (7 score + 1 gate)
  - GET /settings: screener_settings 싱글톤 row 조회
  - PUT /settings: 가중치/노드/게이트 파라미터 round-trip
- main.py: screener_router include (FastAPI 생성 직후)
- db.py: STOCK_DB_PATH 환경변수 지원 (테스트 격리, 기본값 /app/data/stock.db 유지)
- test_screener_router.py: 3 tests (nodes list, settings GET, PUT round-trip)

stock-lab/app/main.py

@@ -27,6 +27,10 @@ from .ai_summarizer import summarize_news, OllamaError
 
 app = FastAPI()
 
+# Screener 라우터 등록
+from app.screener.router import router as screener_router
+app.include_router(screener_router)
+
 # CORS 설정 (프론트엔드 접근 허용)
 _cors_origins = os.getenv("CORS_ALLOW_ORIGINS", "http://localhost:3007,http://localhost:8080").split(",")
 app.add_middleware(