Add missing color_palette.svg (Design colour-tool icon)

DesignPanel's per-body colour button references icon "color_palette" but the
asset was never ported with the CAD subsystem. On mainline OrcaSlicer the
missing bitmap throws during MainFrame construction → segfault at startup
(create_scaled_bitmap "Could not load bitmap: color_palette"). Copied from
snaporca-cad resources; runtime-loaded, no rebuild needed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BVzKmX6Y1aEteit1HTXG4Q

resources/images/color_palette.svg

@@ -0,0 +1,14 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g clip-path="url(#clip0_23434_47713)">
+<circle cx="9.32187" cy="4.2125" r="0.9" fill="#009688"/>
+<circle cx="3.65625" cy="8.75" r="0.75" fill="#009688"/>
+<path d="M8 0.5C12.0195 0.5 15.2656 3.35278 15.4824 6.74512L15.4932 7.0752C15.4914 9.23822 13.7134 11.0155 11.5498 11.0156H9.95312C9.71275 11.0126 9.4739 11.0574 9.25098 11.1475C9.0257 11.2386 8.82126 11.3741 8.64941 11.5459C8.47744 11.7179 8.34113 11.9229 8.25 12.1484C8.1817 12.3176 8.13909 12.4957 8.12402 12.6768L8.11816 12.8496C8.11817 13.3362 8.27448 13.7495 8.59473 14.0801V14.0811C8.73012 14.2338 8.81831 14.4375 8.81836 14.6494C8.81836 15.1395 8.45218 15.5 8 15.5C3.87614 15.5 0.5 12.1239 0.5 8C0.5 3.87614 3.87614 0.5 8 0.5Z" stroke="#949494" stroke-linecap="round" stroke-linejoin="round"/>
+<circle cx="5.17031" cy="5.11172" r="1.35" fill="#009688"/>
+<circle cx="12.1578" cy="7.10313" r="1.15" fill="#009688"/>
+</g>
+<defs>
+<clipPath id="clip0_23434_47713">
+<rect width="16" height="16" fill="white"/>
+</clipPath>
+</defs>
+</svg>