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/screener/router.py

@@ -0,0 +1,85 @@
+"""FastAPI router for /api/stock/screener/*"""
+
+from __future__ import annotations
+
+import datetime as dt
+import json
+import os
+import sqlite3
+
+from fastapi import APIRouter, HTTPException
+
+from . import schemas
+from .registry import NODE_REGISTRY, GATE_REGISTRY
+
+
+router = APIRouter(prefix="/api/stock/screener")
+
+
+def _db_path() -> str:
+    return os.environ.get("STOCK_DB_PATH", "/app/data/stock.db")
+
+
+def _conn() -> sqlite3.Connection:
+    return sqlite3.connect(_db_path())
+
+
+# ---------- /nodes ----------
+
+@router.get("/nodes", response_model=schemas.NodesResponse)
+def get_nodes():
+    score_nodes = [
+        schemas.NodeMeta(
+            name=cls.name, label=cls.label,
+            default_params=cls.default_params, param_schema=cls.param_schema,
+        )
+        for cls in NODE_REGISTRY.values()
+    ]
+    gate_nodes = [
+        schemas.NodeMeta(
+            name=cls.name, label=cls.label,
+            default_params=cls.default_params, param_schema=cls.param_schema,
+        )
+        for cls in GATE_REGISTRY.values()
+    ]
+    return schemas.NodesResponse(score_nodes=score_nodes, gate_nodes=gate_nodes)
+
+
+# ---------- /settings ----------
+
+@router.get("/settings", response_model=schemas.SettingsResponse)
+def get_settings():
+    with _conn() as c:
+        row = c.execute(
+            "SELECT weights_json, node_params_json, gate_params_json, "
+            "top_n, rr_ratio, atr_window, atr_stop_mult, updated_at "
+            "FROM screener_settings WHERE id=1"
+        ).fetchone()
+    if row is None:
+        raise HTTPException(503, "settings not initialized")
+    return schemas.SettingsResponse(
+        weights=json.loads(row[0]),
+        node_params=json.loads(row[1]),
+        gate_params=json.loads(row[2]),
+        top_n=row[3], rr_ratio=row[4], atr_window=row[5], atr_stop_mult=row[6],
+        updated_at=row[7],
+    )
+
+
+@router.put("/settings", response_model=schemas.SettingsResponse)
+def put_settings(body: schemas.SettingsBody):
+    now = dt.datetime.utcnow().isoformat()
+    with _conn() as c:
+        c.execute(
+            """UPDATE screener_settings SET
+               weights_json=?, node_params_json=?, gate_params_json=?,
+               top_n=?, rr_ratio=?, atr_window=?, atr_stop_mult=?, updated_at=?
+               WHERE id=1""",
+            (
+                json.dumps(body.weights), json.dumps(body.node_params),
+                json.dumps(body.gate_params),
+                body.top_n, body.rr_ratio, body.atr_window, body.atr_stop_mult, now,
+            ),
+        )
+        c.commit()
+    return schemas.SettingsResponse(**body.model_dump(), updated_at=now)