Add DipTrace PCB XML parser

[CTEC-2025]

Summary

• add native DipTrace PCB XML support for .dip and .dipxml files
• parse components, embedded patterns, pads, board outlines, silkscreen geometry, nets, tracks, and copper pours
• normalize DipTrace mm, mil, and inch units to the InteractiveHtmlBom coordinate model
• add parser smoke-test fixtures and document DipTrace support

Validation

• Python compileall passes
• direct smoke tests pass for both .dip and .dipxml, including unit conversion
• pytest was not available in the bundled runtime

DipTrace XML format reference: https://www.diptrace.com/support/tutorials/xml_specs_PCB_html/

[qu1ck]

pytest was not available in the bundled runtime

Tell your AI to hold your horses for a bit. I will be adding a test suite for kicad parser soon and would like to see similar full test coverage in new parser too.

I will ping this MR when ready.