Crashes if columns have defined enums

[richardmaw-codethink]

Describe the bug

mkdocs-dbml raises an exception pointing to

mkdocs-dbml/mkdocs_dbml_plugin/renderer.py

Line 391 in 8a59d9f

if len(type_text) > 15:

because the column type is Enum which doesn't implement len.

To reproduce

1. Add plugin to mkdocs.yml: ...
2. Put DBML containing enums in a page
3. Run mkdocs serve
4. See error / wrong diagram

Expected behavior
DBML tables rendered.

Environment

• OS: Linux, but should happen on any.
• Python: 3.13, but should happen on any
• MkDocs: 1.6.1
• mkdocs-dbml-plugin: Latest, but appears to be present as far back as 1.0.0

Additional context

The type of columns is defined to be str | Enum at https://github.com/Vanderhoof/PyDBML/blob/04d19974193a9bb173436dab53b94ecc2919fd58/pydbml/_classes/column.py#L25

It it converted from string form to Enum in https://github.com/Vanderhoof/PyDBML/blob/04d19974193a9bb173436dab53b94ecc2919fd58/pydbml/parser/blueprints.py#L146

Enums implement str (https://github.com/Vanderhoof/PyDBML/blob/04d19974193a9bb173436dab53b94ecc2919fd58/pydbml/_classes/enum.py#L81) and str.str reflexively returns itself so type_text = str(column.type) should fix that.