feat: add PDIP, SPDIP, and UTDFN-EP footprints

[AdityaSinghBiztech]

Summary

Implements three missing footprint packages:

• PDIP (fixes Implement PDIP-8 #371): Plastic DIP — aliases the existing DIP generator; pdip8, pdip14, etc.
• SPDIP (fixes Implement SPDIP-28 #180): Shrink Plastic DIP — uses 70 mil (1.778 mm) pitch, 300 mil row spacing; spdip28, spdip16, etc.
• UTDFN (fixes Implement UTDFN-4-EP(1x1) #183): Ultra-Thin DFN with Exposed Pad — defaults to 4-EP(1×1mm), 0.5 mm pitch, includes exposed pad; utdfn4, etc.

Note: SOT-223-5 (#181) is already implemented via the existing sot223 function — footprinter.string("sot223_5") resolves correctly.

Test plan

• pdip8, pdip14 generate correct plated-hole layout
• spdip28, spdip16 generate 70-mil pitch DIP layout
• utdfn4 generates 4 signal pads + 1 exposed pad with corner silkscreen
• Format and type checks pass

🤖 Generated with Claude Code

[singhaditya21]

Superseded by PR #666 (same changes, from my correct GitHub account singhaditya21). Please close this PR.

[singhaditya21]

This PR is a duplicate — please close in favour of #666 which is the same implementation submitted from the correct account (singhaditya21).

[di3go04]

The test failures are caused by this PR being based on an older version of main. The parity test snapshots and infrastructure have been updated on main but the PR's branch still has the old versions.

Fix: Merge main into your branch (\git merge main). This will:

• Update the \package.json\ version and dependencies
• Update the \compareFootprinterVsKicad.ts\ test infrastructure
• Apply the updated snapshots across all parity tests

I verified locally that merging main resolves all 73+ failing parity tests (all pass after merge). The PR's new footprint generators continue to work correctly.