fix: resolve signed/unsigned integer comparison warning

- Use static_cast<size_t>() to convert view_of_partition->length to unsigned type
- Fixes modernize-use-integer-sign-comparison clang-tidy warning at line 375
- Safe conversion since Arrow array lengths are always non-negative

Author: HeartLinked

src/iceberg/manifest_reader_internal.cc

@@ -372,7 +372,8 @@ Status ParseDataFile(const std::shared_ptr<StructType>& data_file_schema,
         }
         if (view_of_file_field->n_children > 0) {
           auto view_of_partition = view_of_file_field->children[0];
-          for (size_t row_idx = 0; row_idx < view_of_partition->length; row_idx++) {
+          for (size_t row_idx = 0;
+               row_idx < static_cast<size_t>(view_of_partition->length); row_idx++) {
             if (ArrowArrayViewIsNull(view_of_partition, row_idx)) {
               break;
             }