perf: replace dyn trait objects with concrete types to eliminate vtable overhead

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

src/application/ports/outbound.rs

@@ -1,4 +1,3 @@
-use async_trait::async_trait;
 use std::path::PathBuf;
 
 use crate::common::errors::DomainError;
@@ -10,7 +9,6 @@ pub use crate::domain::repositories::folder_repository::FolderRepository;
 use super::storage_ports::{FileReadPort, FileWritePort};
 
 /// Secondary port for storage operations
-#[async_trait]
 pub trait StoragePort: Send + Sync + 'static {
     /// Resolves a domain path to a physical path
     fn resolve_path(&self, storage_path: &StoragePath) -> PathBuf;