feat(ugc): color_brightness and transparent_colors

color_brightness (percent, default 100: unchanged) scales the models' vertex
colors, not the icons', for servers where the made models look brighter than
they should. transparent_colors names color ids drawn transparent whatever
Materials.xml says: 129 (Tr. Bright Bluish Violet with Glitter) has alpha
255 there, so it came out opaque; a named color gets transparent_opacity.
Both default to off, so models come out byte for byte as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dUgcServer/UgcModel.h

@@ -3,6 +3,7 @@
 #include <array>
 #include <cstdint>
 #include <map>
+#include <set>
 #include <optional>
 #include <string>
 #include <string_view>
@@ -93,6 +94,8 @@ namespace UgcModel {
 		float colorVariation{ 5.0f };      // percent, 0: none (LU Toolbox: Apply Color Variation, 5%)
 		uint64_t seed{};                   // of the variation's random numbers
 		float transparentOpacity{ 58.82f }; // percent, transparent bricks' vertex alpha (LU Toolbox palette only)
+		float brightness{ 100.0f };        // percent, the models' vertex colors (not icons'); 100: as the palette has them
+		std::set<uint32_t> transparentColors; // color ids drawn transparent whatever Materials.xml says (129: its alpha is 255)
 		bool icon{};                       // the icon renderer's color corrections
 		uint32_t lod{};                    // brickprimitives level
 		LookRules looks;                   // which colors are metal and glow (Mesh::looks)