Add Prindle microfluidic device source files

[marpaia]

Purpose

Isolate the large Prindle device source artifacts from all code and prose review.

Methodological contribution

None in this PR. It contains only the source artifacts and their provenance note:

• docs/tutorials/devices/README.md
• docs/tutorials/devices/prindle.dwg
• docs/tutorials/devices/prindle.dxf

The 413,362-line DXF remains in its own PR so it cannot obscure review of walls, flow, coupling, or tutorials.

Provenance and interpretation boundary

• Gonzalo Vidal provided these files to Mike Arpaia for inclusion and redistribution in this DRAGGON Lab project. DRAGGON Lab is Gonzalo Vidal's research group at the University of Bristol. The adjacent README records that provenance; no additional provenance metadata is required for this merge.
• PR Add microfluidic device and biology tutorials #6 now treats physical scale as a documented inference specific to this file: raw dimensions of 0.100 and a row pitch of 0.125 correspond to the published 100-micrometer trap dimension plus 25-micrometer spacing under a 1,000 micrometers-per-drawing-unit conversion. The file's $INSUNITS=1 insertion metadata is not treated as an authoritative unit declaration.
• PR Add microfluidic device and biology tutorials #6 does not derive cavity walls or layer thicknesses from these assets and does not assert that this is the exact fabrication revision used in the publication. The substantial unplaced Layer-5 block geometry is left without a physical-layer assignment because no process map accompanies the files.
• The DWG-to-DXF conversion recipe, embedded workstation path, checksums, and Git-versus-LFS choice are archival or maintenance concerns rather than merge blockers. The files remain unchanged in ordinary Git.

Stack

PR 4 of 5.

Base: #4 (marpaia/microfluidics-experimental-coupling)

Next: #6 (marpaia/microfluidics-tutorials)