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/interfaces/api/routes.rs

@@ -8,6 +8,7 @@ use axum::{
 use serde_json::json;
 use std::sync::Arc;
 use tower_http::{compression::CompressionLayer, trace::TraceLayer};
+use crate::application::services::batch_operations::BatchOperationService;
 
 /// Returns the application version from Cargo.toml (compile-time constant)
 async fn get_version() -> AxumJson<serde_json::Value> {
@@ -17,7 +18,6 @@ async fn get_version() -> AxumJson<serde_json::Value> {
     }))
 }
 
-use crate::application::services::batch_operations::BatchOperationService;
 
 use crate::interfaces::api::handlers::admin_handler;
 use crate::interfaces::api::handlers::batch_handler::{self, BatchHandlerState};