build: update Cargo.toml edition

* The edition in Cargo.toml was updated from 2021 to 2024.

Author: Thomas Oppelt

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "convcom"
 version = "0.1.0"
-edition = "2021"
+edition = "2024"
 description = "AI-powered conventional commit message generator using Groq and Anthropic APIs"
 keywords = ["git", "commit", "ai", "conventional-commits", "groq"]
 categories = ["command-line-utilities", "development-tools"]