refactor: rename stock-lab → stock (graduation)

- git mv stock-lab/ → stock/
- docker-compose.yml: 서비스 키 + container_name + build.context +
  frontend.depends_on + agent-office STOCK_LAB_URL → STOCK_URL
- agent-office/app: config.py, service_proxy.py, agents/stock.py, tests/
  STOCK_LAB_URL → STOCK_URL
- nginx/default.conf: proxy_pass http://stock-lab → http://stock (3 lines)
- CLAUDE.md / README.md / STATUS.md / scripts/ 문구 갱신
- stock/ 내부 자기 참조 갱신

lab 네이밍 정책 (feedback_lab_naming.md) graduation.
API URL / Python import / DB 파일명 변경 없음.

stock/app/test_screener_nodes_base.py

@@ -0,0 +1,24 @@
+import pandas as pd
+import pytest
+
+from app.screener.nodes.base import percentile_rank
+
+
+def test_percentile_rank_basic():
+    s = pd.Series([10, 20, 30, 40, 50])
+    out = percentile_rank(s)
+    assert (out >= 0).all() and (out <= 100).all()
+    assert out.iloc[0] < out.iloc[-1]                  # smallest gets lowest rank
+
+
+def test_percentile_rank_all_equal_returns_50():
+    s = pd.Series([42, 42, 42, 42])
+    out = percentile_rank(s)
+    assert (out == 50.0).all()
+
+
+def test_percentile_rank_handles_nan():
+    s = pd.Series([1.0, float("nan"), 3.0, 5.0])
+    out = percentile_rank(s)
+    assert pd.isna(out.iloc[1])
+    assert (out.dropna() >= 0).all()