Clean up repository: remove planning docs and organize structure

Add network pre-computation, styling improvements, and theme toggle

Add force-directed graph UI controls, rounded points, growth rate calculation, and error handling improvements

Add 3D force-directed graph with instanced rendering and pre-computed positions

Add 150k model support, background computation, demo GIF, and UI improvements

Refactor UI: Stack Sans font, remove rounded corners, consolidate navigation

Apply clean grayscale design, remove all emojis