props: add RustChain GPU farm prop

pk3_build/models/props/rustchain_gpu_farm/LICENSE

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+RustChain GPU Farm prop
+
+Copyright 2026
+
+This model, texture pack, preview image, and source mesh are licensed under
+the Creative Commons Attribution-ShareAlike 4.0 International License
+(CC-BY-SA-4.0).
+
+License summary and legal code:
+https://creativecommons.org/licenses/by-sa/4.0/

pk3_build/models/props/rustchain_gpu_farm/README.md

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+# RustChain GPU Farm prop
+
+Original low-poly static prop for the Xonotic RustChain Arena prop bounty #14015:
+https://github.com/Scottcjn/rustchain-bounties/issues/14015
+
+## Package
+
+| File | Purpose |
+| --- | --- |
+| `rustchain_gpu_farm.iqm` | Static IQM model for a compact mining rig / GPU farm |
+| `rustchain_gpu_farm_0.skin` | DarkPlaces/Xonotic material-to-texture mapping |
+| `gpu_farm_frame.tga` | 256x256 dark rack frame texture |
+| `gpu_farm_boards.tga` | 256x256 teal GPU board texture |
+| `gpu_farm_fans.tga` | 256x256 cyan fan glow texture |
+| `gpu_farm_cables.tga` | 256x256 orange cable texture |
+| `rustchain_gpu_farm_preview.png` | Preview render with material swatches |
+| `rustchain_gpu_farm_source.obj` | Editable source mesh |
+| `rustchain_gpu_farm_source.mtl` | Source material table |
+
+## Design
+
+This model covers the **mining rig / GPU farm** wishlist item. It is a small
+arena set-dressing prop with a two-tier metal rack, six visible GPU boards,
+cyan fan hubs, orange power cables, and a raised RTC hash light bar. The shape
+is intentionally compact so map authors can use it as cover, background tech,
+or a cluster near a validator room.
+
+The geometry and textures are procedural and original. No external meshes,
+samples, texture packs, or AI model files are embedded.

pk3_build/models/props/rustchain_gpu_farm/rustchain_gpu_farm_0.skin

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+rig_frame,models/props/rustchain_gpu_farm/gpu_farm_frame
+gpu_board,models/props/rustchain_gpu_farm/gpu_farm_boards
+fan_glow,models/props/rustchain_gpu_farm/gpu_farm_fans
+rtc_cable,models/props/rustchain_gpu_farm/gpu_farm_cables

pk3_build/models/props/rustchain_gpu_farm/rustchain_gpu_farm_source.mtl

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+newmtl rig_frame
+Kd 0.150 0.160 0.180
+map_Kd gpu_farm_frame.tga
+
+newmtl gpu_board
+Kd 0.080 0.340 0.310
+map_Kd gpu_farm_boards.tga
+
+newmtl fan_glow
+Kd 0.060 0.700 0.760
+map_Kd gpu_farm_fans.tga
+
+newmtl rtc_cable
+Kd 0.850 0.420 0.100
+map_Kd gpu_farm_cables.tga