The icon enum, its URIs and bytes now come from fastframe-icons' icons!
macro, and the 43 Lucide icons Spotifast shares byte for byte with ZapFast
come from the crate instead of assets/icons (four of them were not in use
here). Spotifast's own icons keep their files and their names.
Behaviour change: icons are served by the crate's loader, which keeps
their bytes for the life of the window instead of handing them to
ctx.include_bytes. Nothing changes today; it prevents red placeholders
where an icon drawn at a second size lost its bytes if egui's
reduce_texture_memory were ever turned on.