Fix: API import 및 디렉토리 구조 수정

front/src/App.jsx

front/src/api/routineAPI.js

front/src/api/workoutAPI.js

front/src/assets/explains.json

front/src/components/Footer.jsx

front/src/components/Header.jsx

front/src/components/Resizable.jsx

front/src/components/common/ExerciseBlock.jsx

front/src/components/common/Thumbnails.jsx

front/src/components/routine/List.css

front/src/components/routine/List.jsx

front/src/components/routine/Now.css

front/src/components/routine/Now.jsx

front/src/components/routine/Progress.jsx

front/src/components/routine/Rest.css

front/src/components/routine/Rest.jsx

front/src/components/routine/Start.css

front/src/components/routine/Start.jsx

front/src/components/routine/Timer.css

front/src/components/routine/Timer.jsx