Rust edition 2024; drop mod.rs for module-named files

Workspace, vtracer-py, and the nodejs wasm crate move from edition 2021
to 2024 (no code changes needed — clean build and test run on 1.95).
Module directories switch from foo/mod.rs to the modern foo.rs layout;
single-file modules (svg, optimize, compose, fitter) collapse from
directories into plain files. Pure git renames, history preserved.

crates/vtracer-py/Cargo.toml

@@ -3,7 +3,7 @@ name = "vtracer-py"
 description = "Python bindings for the vtracer vectorization framework."
 version = "1.0.0-alpha.1"
 authors = ["Chris Tsang <tyt2y7@gmail.com>"]
-edition = "2021"
+edition = "2024"
 license = "MIT OR Apache-2.0"
 homepage = "http://www.visioncortex.org/vtracer"
 repository = "https://github.com/visioncortex/vtracer/"