fix: avoid integer overflow when multiplying received image width by height

This is a minor fix, worst case an image with very large dimensions will not be classified as a File.
Mostly removing `clippy::arithmetic_side_effects`.

src/mimeparser.rs

@@ -1490,7 +1490,6 @@ impl MimeMessage {
     }
 
     #[expect(clippy::too_many_arguments)]
-    #[expect(clippy::arithmetic_side_effects)]
     async fn do_add_single_file_part(
         &mut self,
         context: &Context,
@@ -1565,7 +1564,11 @@ impl MimeMessage {
         {
             match get_filemeta(decoded_data) {
                 // image size is known, not too big, keep msg_type:
-                Ok((width, height)) if width * height <= constants::MAX_RCVD_IMAGE_PIXELS => {
+                Ok((width, height))
+                    if width
+                        .checked_mul(height)
+                        .is_some_and(|pixels| pixels <= constants::MAX_RCVD_IMAGE_PIXELS) =>
+                {
                     part.param.set_i64(Param::Width, width.into());
                     part.param.set_i64(Param::Height, height.into());
                     msg_type