style: apply rustfmt to backend codebase

- Apply rustfmt to all Rust source files in backend/
- Fix trailing whitespace inconsistencies
- Standardize formatting across handlers, models, and services
- Improve code readability with consistent formatting

These changes are purely stylistic and do not affect functionality.
All CI checks now pass with proper formatting.

backend/src/handlers/mod.rs

@@ -1,20 +1,28 @@
 pub mod auth;
 pub mod health;
 pub mod health_stats;
+pub mod interactions;
+pub mod medications;
 pub mod permissions;
+pub mod sessions;
 pub mod shares;
 pub mod users;
-pub mod sessions;
-pub mod medications;
-pub mod interactions;
 
 // Re-export commonly used handler functions
-pub use auth::{register, login, recover_password};
+pub use auth::{login, recover_password, register};
 pub use health::{health_check, ready_check};
-pub use shares::{create_share, list_shares, update_share, delete_share};
-pub use permissions::check_permission;
-pub use users::{get_profile, update_profile, delete_account, change_password, get_settings, update_settings};
-pub use sessions::{get_sessions, revoke_session, revoke_all_sessions};
-pub use medications::{create_medication, list_medications, get_medication, update_medication, delete_medication, log_dose, get_adherence};
-pub use health_stats::{create_health_stat, list_health_stats, get_health_stat, update_health_stat, delete_health_stat, get_health_trends};
+pub use health_stats::{
+    create_health_stat, delete_health_stat, get_health_stat, get_health_trends, list_health_stats,
+    update_health_stat,
+};
 pub use interactions::{check_interactions, check_new_medication};
+pub use medications::{
+    create_medication, delete_medication, get_adherence, get_medication, list_medications,
+    log_dose, update_medication,
+};
+pub use permissions::check_permission;
+pub use sessions::{get_sessions, revoke_all_sessions, revoke_session};
+pub use shares::{create_share, delete_share, list_shares, update_share};
+pub use users::{
+    change_password, delete_account, get_profile, get_settings, update_profile, update_settings,
+};