Embed shader resources with C++26 - #14

Summary

• replace Qt RCC shader storage with C++26
• expose one static shader/colormap source registry to Qt and ImGui frontends
• patch the pinned colormap-shaders subproject to provide source assets without linking Qt
• reject visualization configurations whose compiler cannot compile the embedded sources

Verification

• GCC 15 feature probe passes
• Qt-free visualization configuration succeeds
• changed shader and pipeline translation units compile in Qt and Qt-free builds
• all 104 compatible colormaps resolve; representative image and scalar-field shaders compile through shaderc
• visualization-disabled build completes

Known unrelated blocker

The complete visualization build currently fails against quiver main because balsa still uses older AABB/KDOP/BVH template signatures. This predates and is independent of the shader storage changes.