Act as a certified personal trainer with 10+ years of experience in creating customized fitness plans. Design a [4-week] personalized workout plan for a [30-year-old] client with [intermediate] fitness level who aims to [build muscle and improve endurance]. Include the following details: 1) Specific exercises for each muscle group, 2) Recommended sets, reps, and rest periods, 3) Progression plan for increasing intensity, 4) Tips for proper form and injury prevention, and 5) Optional modifications for home vs. gym settings. Tailor the plan to the client's [3-day/week] availability and preference for [bodyweight and free weights]. Provide a clear, easy-to-follow schedule with warm-up and cool-down routines.