Remove async-trait dependency and use native Rust async fn in traits.
Replace Arc<dyn Trait> with Arc<ConcreteType> throughout the codebase
to enable monomorphization and eliminate dynamic dispatch overhead.
Key changes:
- Remove write-behind cache (no implementation existed)
- Fix should_transcode static method call
- Use ContactStorageAdapter directly instead of dyn AddressBookUseCase
- Clean up unused trait imports across services and DI
https://claude.ai/code/session_01EbAFEfyJNLRmJHmmYDX3Tt
Standardize code formatting across all 173 Rust source files
using rustfmt. No functional changes - purely cosmetic.
This establishes a consistent code style baseline for the
project going forward.