style: apply cargo fmt to entire codebase

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.

src/application/dtos/address_book_dto.rs

@@ -1,6 +1,6 @@
+use crate::domain::entities::contact::AddressBook;
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
-use crate::domain::entities::contact::AddressBook;
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AddressBookDto {
@@ -73,4 +73,4 @@ pub struct ShareAddressBookDto {
 pub struct UnshareAddressBookDto {
     pub address_book_id: String,
     pub user_id: String,
-}
+}