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/middleware/auth.rs

@@ -1,11 +1,11 @@
+use crate::auth::jwt::Claims;
+use crate::config::AppState;
 use axum::{
     extract::{Request, State},
     http::StatusCode,
     middleware::Next,
     response::Response,
 };
-use crate::auth::jwt::Claims;
-use crate::config::AppState;
 
 pub async fn jwt_auth_middleware(
     State(state): State<AppState>,
@@ -13,29 +13,29 @@ pub async fn jwt_auth_middleware(
     next: Next,
 ) -> Result<Response, StatusCode> {
     let headers = req.headers();
-    
+
     // Extract Authorization header
     let auth_header = headers
         .get("Authorization")
         .and_then(|h| h.to_str().ok())
         .ok_or(StatusCode::UNAUTHORIZED)?;
-    
+
     // Check Bearer token format
     if !auth_header.starts_with("Bearer ") {
         return Err(StatusCode::UNAUTHORIZED);
     }
-    
+
     let token = &auth_header[7..]; // Remove "Bearer " prefix
-    
+
     // Verify token
     let claims = state
         .jwt_service
         .validate_token(token)
         .map_err(|_| StatusCode::UNAUTHORIZED)?;
-    
+
     // Add claims to request extensions for handlers to use
     req.extensions_mut().insert(claims);
-    
+
     Ok(next.run(req).await)
 }