feat(footprinter): implement UTDFN-4-EP(1x1) footprint

[KrishnaX12]

Fixes #183

Summary

Adds support for the UTDFN-4-EP (1×1mm) windmill land pattern footprint, following the SGM2036 recommended land pattern and matching KiCad's UDFN-4-1EP_1x1mm_P0.65mm_EP0.48x0.48mm standard.

Changes

• src/fn/utdfn.ts: Implemented utdfn footprint with configurable dimensions, 45° rotated thermal pad diamond, and chamfered corner pads.
• src/fn/dfn.ts: Extracted shared getDfnCornerPadPoints helper for chamfered pad reuse.
• src/footprinter.ts: Added utdfn builder and aliases (utdfn_4_ep, UTDFN-4-EP, UTDFN-4-EP(1x1)).
• Tests: Added unit tests (tests/utdfn.test.ts) and KiCad parity verification (tests/kicad-parity/utdfn4-kicad-parity.test.ts).

Verification

• KiCad Parity: Boolean difference test against KiCad's reference geometry achieves 0.00% diff and 100% courtyard IoU (note: KiCad models these pads as an anchor rectangle plus custom polygon primitives; their union forms the full 1.30mm windmill span).

[techmannih]

Is this single footprint, can you add more variant

[KrishnaX12]

Is this single footprint, can you add more variant

This PR targets UTDFN-4-EP(1x1) specifically, as requested in #183. The builder already allows overriding pitch, pad sizes, span, package dimensions, and thermal-pad dimensions. Could
you specify which additional named UTDFN variants you’d like included?