浏览器太阳系探索器：8颗行星、20颗卫星与飞行规划器

Build an interactive solar system explorer that runs in the browser with Three.js and WebGL. Show the Sun, eight planets and about twenty moons on orbit lines, with textured spheres and Saturn's rings. Use a dark, minimal interface: a left list of bodies to select, a large title and a short description with key stats at the bottom of the view, and a right panel for a simplified spaceflight planner where the user picks a origin and destination and sees an estimated travel time in days. Selecting a body makes the camera glide smoothly from the system overview to a close view of it, and the user can also orbit and zoom the camera freely. Keep planets and moons moving along their orbits. Deliver a working web page with all assets loaded locally or procedurally. Done means you can fly from the Sun to Earth, its Moon and Saturn, read the stats, and get a travel estimate between two planets.