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/carddav_ports.rs

@@ -7,11 +7,9 @@ use crate::application::dtos::contact_dto::{
     GroupMembershipDto, UpdateContactDto, UpdateContactGroupDto,
 };
 use crate::common::errors::DomainError;
-use async_trait::async_trait;
 
 pub type CardDavRepositoryError = DomainError;
 
-#[async_trait]
 pub trait AddressBookUseCase: Send + Sync + 'static {
     // Address Book operations
     async fn create_address_book(
@@ -57,7 +55,6 @@ pub trait AddressBookUseCase: Send + Sync + 'static {
     ) -> Result<Vec<(String, bool)>, DomainError>;
 }
 
-#[async_trait]
 pub trait ContactUseCase: Send + Sync + 'static {
     // Contact operations
     async fn create_contact(&self, dto: CreateContactDto) -> Result<ContactDto, DomainError>;