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.
- Implemented `OKDLoadBalancerScore` and integrated it as a `FrontendScore`.
- Added `FrontendScore` trait for TUI displayable scores.
- Implemented `Display` for `OKDLoadBalancerScore`.
- Updated `ScoreListWidget` to handle `FrontendScore` types.
- Included load balancer score in the TUI.
