Implement configurable logging with tracing

- Replace eprintln! with tracing macros for configurable log levels
- Set up tracing_subscriber with level filtering from config
- Log format: YYYY-MM-DDTHH:MM:SSZ LEVEL IP "request" STATUS "message"
- Success logs: INFO level for 20 responses
- Error logs: WARN for 41/51, ERROR for 59
- Rate limiting and file serving now properly logged
- Remove unused RequestLogger::log_success method

src/server.rs

@@ -17,10 +17,17 @@ pub async fn serve_file(
 ) -> io::Result<()> {
     if file_path.exists() && file_path.is_file() {
         let mime_type = get_mime_type(file_path);
+        let header = format!("20 {}\r\n", mime_type);
+        stream.write_all(header.as_bytes()).await?;
+        // Log success after sending header
+        let client_ip = match stream.get_ref().0.peer_addr() {
+            Ok(addr) => addr.to_string(),
+            Err(_) => "unknown".to_string(),
+        };
+        tracing::info!("{} \"file:{}\" 20 \"Success\"", client_ip, file_path.display());
+        // Then send body
         let content = fs::read(file_path)?;
-        let mut response = format!("20 {}\r\n", mime_type).into_bytes();
-        response.extend(content);
-        stream.write_all(&response).await?;
+        stream.write_all(&content).await?;
         stream.flush().await?;
         Ok(())
     } else {
@@ -118,10 +125,12 @@ pub async fn handle_connection(
 
             // Serve the file
             match serve_file(&mut stream, &file_path).await {
-                Ok(_) => logger.log_success(20),
+                Ok(_) => {
+                    // Success already logged in serve_file
+                }
                 Err(_) => {
-                    // This shouldn't happen since we check existence, but handle gracefully
-                    logger.log_error(51, "File not found");
+                    // File transmission failed
+                    logger.log_error(51, "File transmission failed");
                     let _ = send_response(&mut stream, "51 Not found\r\n").await;
                 }
             }
@@ -155,7 +164,6 @@ pub async fn handle_connection(
     }
 
     ACTIVE_REQUESTS.fetch_sub(1, Ordering::Relaxed);
-    eprintln!("DEBUG: Request completed, count decremented");
     Ok(())
 }