feat: Add core models and protocol definitions for NxMesh

crates/nxmesh-core/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "nxmesh-core"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+serde.workspace = true
+serde_json.workspace = true
+thiserror.workspace = true
+chrono.workspace = true
+uuid.workspace = true
+
+[dev-dependencies]
+tokio-test.workspace = true