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.

agent-office/tests/test_stock_screener_job.py

@@ -1,6 +1,6 @@
 """StockAgent.on_screener_schedule — 평일 16:30 KST 자동 잡 단위 테스트.
 
-stock-lab HTTP 호출은 service_proxy mock, 텔레그램은 messaging.send_raw mock.
+stock HTTP 호출은 service_proxy mock, 텔레그램은 messaging.send_raw mock.
 """
 import os
 import sys
@@ -138,7 +138,7 @@ def test_screener_run_failure_notifies_operator():
     from app.telegram import messaging
 
     fake_snap = AsyncMock(return_value={"status": "ok"})
-    fake_run = AsyncMock(side_effect=RuntimeError("stock-lab 500"))
+    fake_run = AsyncMock(side_effect=RuntimeError("stock 500"))
     fake_send = AsyncMock(return_value={"ok": True, "message_id": 1})
 
     with patch.object(service_proxy, "refresh_screener_snapshot", fake_snap), \