fix(map): S57EncOverlay API URL을 공유 API_BASE_URL로 통합

- VITE_API_URL 하드코딩 제거 → @common/services/api의 API_BASE_URL 사용

frontend/src/common/components/map/S57EncOverlay.tsx

@@ -1,8 +1,8 @@
 import { useEffect, useRef } from 'react';
 import { useMap } from '@vis.gl/react-maplibre';
+import { API_BASE_URL } from '../../services/api';
 
-const TILES_BASE = import.meta.env.VITE_API_URL?.replace(/\/api$/, '') || 'http://localhost:3001';
-const PROXY_PREFIX = `${TILES_BASE}/api/tiles/enc`;
+const PROXY_PREFIX = `${API_BASE_URL}/tiles/enc`;
 
 const ENC_SPRITE_ID = 'enc-s57';
 const ENC_SOURCE_ID = 'enc-s57';