TruncateTransform.satisfies_order_of raises AttributeError for different widths

### Apache Iceberg version

0.11.0 (latest release)

### Please describe the bug 🐞

### Description

Calling `TruncateTransform.satisfies_order_of` with two valid truncate transforms that have different widths raises an `AttributeError` instead of returning a boolean.

Same-width comparisons work because the method returns early when the transforms are equal.

### Reproduction

```python
from pyiceberg.transforms import TruncateTransform

TruncateTransform(5).satisfies_order_of(TruncateTransform(3))
```

On `main` at commit `48e710d20ceeeaa637d5aeae7746b787410859f8`, this raises:

```text
AttributeError: 'TruncateTransform' object has no attribute '_source_type'
```

The failure reproduces consistently. The same code is also present in the 0.11.1 release.

### Expected behavior

The method should compare the truncate widths and return a boolean:

```python
assert TruncateTransform(5).satisfies_order_of(TruncateTransform(3))
assert not TruncateTransform(3).satisfies_order_of(TruncateTransform(5))
```

This matches the current Apache Iceberg Java implementation:

https://github.com/apache/iceberg/blob/25654ab4b29c8b5b5c20fc427da01cb70d94ed14/api/src/main/java/org/apache/iceberg/transforms/Truncate.java#L130-L141

### Cause

`TruncateTransform.__init__` initializes `_width` but not `_source_type`. However, `satisfies_order_of` still accesses the `source_type` property backed by `_source_type`:

https://github.com/apache/iceberg-python/blob/48e710d20ceeeaa637d5aeae7746b787410859f8/pyiceberg/transforms.py#L783-L905

The existing unit test only compares a transform with itself, so it returns before reaching the failing branch:

https://github.com/apache/iceberg-python/blob/48e710d20ceeeaa637d5aeae7746b787410859f8/tests/test_transforms.py#L501-L512

A focused fix could compare `TruncateTransform` widths directly, consistent with the Java implementation, and add regression cases for different widths.

I would be happy to contribute the fix and regression tests.

### Willingness to contribute

- [x] I can contribute a fix for this bug independently
- [ ] I would be willing to contribute a fix for this bug with guidance from the Iceberg community
- [ ] I cannot contribute a fix for this bug at this time

Bắt đầu trong pyiceberg/transforms.py tại TruncateTransform.satisfies_order_of và xem xét constructor liên quan cùng thuộc tính source_type. Chạy các trường hợp tập trung trong tests/test_transforms.py quanh các dòng 501-512, sau đó thêm coverage cho các width khác nhau. Hoàn tất khi các phép so sánh trả về các giá trị boolean mong đợi mà không truy cập vào một thuộc tính chưa được khởi tạo.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.