feat: add direct usage example without gRPC

[TobieTom]

Add example demonstrating direct usage of Silius components without gRPC communication.

Changes:

• Add examples/direct/main.rs with single binary implementation
• Add examples/direct/Cargo.toml with dependencies
• Add examples/Cargo.toml for example configuration

This example shows how to use bundler, mempool and RPC components directly in memory, providing a simpler deployment option when service isolation isn't needed.

Resolves #217

[Vid201]

Hey @TobieTom , thanks for opening a PR. I will take a look at it as soon as I can !