feat: add serde derive to Score types

This commit adds `serde` dependency and derives `Serialize` trait for `Score` types. This is necessary for serialization and deserialization of these types, which is required to display Scores to various user interfaces

- Added `serde` dependency to `harmony_types/Cargo.toml`.
- Added `serde::Serialize` derive macro to `MacAddress` in `harmony_types/src/lib.rs`.
- Added `serde::Serialize` derive macro to `Config` in `opnsense-config/src/config/config.rs`.
- Added `serde::Serialize` derive macro to `Score` in `harmony_types/src/lib.rs`.
- Added `serde::Serialize` derive macro to `Config` and `Score` in relevant modules.
- Added placeholder `todo!()` implementations for `serialize` methods. These will be implemented in future commits.

examples/nanodc/src/main.rs

@@ -1,7 +1,10 @@
 use harmony::{
     inventory::Inventory,
     maestro::Maestro,
-    modules::{dummy::{ErrorScore, PanicScore, SuccessScore}, k8s::deployment::K8sDeploymentScore},
+    modules::{
+        dummy::{ErrorScore, PanicScore, SuccessScore},
+        k8s::deployment::K8sDeploymentScore,
+    },
     topology::HAClusterTopology,
 };