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/security/mod.rs

@@ -1,7 +1,7 @@
+pub mod account_lockout;
 pub mod audit_logger;
 pub mod session_manager;
-pub mod account_lockout;
 
+pub use account_lockout::AccountLockout;
 pub use audit_logger::AuditLogger;
 pub use session_manager::SessionManager;
-pub use account_lockout::AccountLockout;