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

[sungdark]

Description

Implements the UTDFN-4-EP(1x1) (Ultra-Thin Dual Flat No-Lead with Exposed Pad, 4-pin, 1x1mm) footprint for the footprinter library.

This footprint supports:

• 4 pins total (2 on each side)
• Body size: 1.0mm x 1.0mm
• Pitch: 0.5mm (default), configurable
• Exposed pad (thermal pad) at the bottom center
• DFN-style silkscreen with pin 1 marker

Bounty

Payment address: ETH 0x5a134107516ecccc83232711efa50eb4e87602c7

Closes #183

[graphite-app]

The exposed pad dimensions are hardcoded and ignore user-provided values. The schema allows ep to be either true or { x: string, y: string }, but when a user provides custom dimensions via the object form, they are completely ignored.

// Current code always uses hardcoded values:
if (parameters.ep) {
  const epw = 0.55
  const eph = 0.35
  pads.push(rectpad(["thermalpad"], 0, 0, epw, eph))
}

// Should handle both cases:
if (parameters.ep) {
  let epw: number, eph: number
  if (typeof parameters.ep === 'object') {
    epw = length.parse(parameters.ep.x)
    eph = length.parse(parameters.ep.y)
  } else {
    epw = 0.55
    eph = 0.35
  }
  pads.push(rectpad(["thermalpad"], 0, 0, epw, eph))
}

This will cause incorrect pad dimensions when users specify custom exposed pad sizes, leading to manufacturing defects.

Suggested change

	if (parameters.ep) {
	const epw = 0.55 // exposed pad width
	const eph = 0.35 // exposed pad height
	pads.push(rectpad(["thermalpad"], 0, 0, epw, eph))
	}
	if (parameters.ep) {
	let epw, eph
	if (typeof parameters.ep === 'object') {
	epw = length.parse(parameters.ep.x)
	eph = length.parse(parameters.ep.y)
	} else {
	epw = 0.55 // exposed pad width
	eph = 0.35 // exposed pad height
	}
	pads.push(rectpad(["thermalpad"], 0, 0, epw, eph))
	}

Spotted by Graphite



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