✨ Refactor: Convert project to a Bevy-based workspace and node

This commit refactors the Vanth project to utilize a `Cargo.toml` workspace,
encapsulating the core logic within a `vanth` library crate. The existing
`src` files are moved into the new `vanth/src` directory.

The primary change is the integration of the Bevy game engine as the
underlying framework for the Vanth node, shifting from the previous
`whirlwind` dependency. This transition is reflected in `Cargo.toml`
updates, adding `bevy_app` and `bevy_ecs` as dependencies and removing
`whirlwind`.

A new test file `vanth/tests/test_node.rs` is introduced to cover the
initial functionality of the `Node` struct. The `LICENSE` year range is
also updated.

This refactoring sets the stage for Vanth's evolution into a distributed
ECS-based database model, leveraging Bevy's robust ECS capabilities.

vanth/tests/test_node.rs

@@ -0,0 +1,7 @@
+use vanth::Node;
+
+#[test]
+fn test_entity_count_zero() {
+    let mut node = Node::new();
+    assert_eq!(node.entity_count(), 0);
+}