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/contact_dto.rs

@@ -1,6 +1,6 @@
+use crate::domain::entities::contact::{Address, Contact, ContactGroup, Email, Phone};
 use chrono::{DateTime, NaiveDate, Utc};
 use serde::{Deserialize, Serialize};
-use crate::domain::entities::contact::{Contact, Email, Phone, Address, ContactGroup};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct EmailDto {
@@ -221,4 +221,4 @@ pub struct UpdateContactGroupDto {
 pub struct GroupMembershipDto {
     pub group_id: String,
     pub contact_id: String,
-}
+}