feat(ugc): make models like LU Toolbox does, within CPU and memory budgets

Parity with LU Toolbox's Process Model, Bake Lighting and icon renderer, with
its defaults as the settings' defaults:

- Colors from its LU palette (UgcPalette: LU colors, LDD colors mapped to the
  nearest LU one, unknown ones black), transparent bricks at 58.82% opacity, a
  brick transparent only when all of its materials are.
- Color variation: each brick's material gets its HSV value shifted in a 2.224
  gamma by up to 5% (times the color's own amount), from a random number of
  the model, brick and material, so reprocessing gives the same colors in
  every LOD. Icons get none, and the icon renderer's color corrections.
- LODs 0 and 2 with its distance logic, written as NiLODNode/NiRangeLODData
  like its exports and the game's own brick models, shapes divided at 65535
  vertices along the longest side like divide_mesh.
- Ambient occlusion like its AO-only bake: 64 rays per vertex, distance 5,
  after hidden surface removal, transparent bricks neither baked nor
  occluding, glow colors added.
- Icons from its icon scene: 50 mm lens at 53.4/19.5 degrees, sun of 2.5 at
  21/50.3 degrees with soft shadows, grey world light with occlusion; LOD 0's
  hidden surface removal and occlusion are reused for them.
- Optional ground plane for hidden surface removal; stats.json per model and
  the previous version's previews kept for comparing.

Budgets, applied live on config reload: max_cpu_percent (workers account
their thread CPU time and sleep to stay under it, long renders included),
worker_nice, max_memory_mb (jobs are estimated from their brick count and
wait until they fit), max_model_bricks and pause_hours. /status and the
traffic report show CPU, memory and throttling.

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

dUgcServer/UgcFormats.h

@@ -26,6 +26,26 @@ namespace UgcFormats {
 	 */
 	std::string WriteNif(const std::string& rootName, const std::vector<NifShape>& shapes);
 
+	struct NifLod {
+		float nearDistance{};
+		float farDistance{};
+		std::string name;                      // the level's node, e.g. LOD_0
+		std::vector<const UgcModel::Mesh*> pieces; // its shapes (UgcModel::Divide's pieces)
+	};
+
+	struct NifLodGroup {
+		std::string name; // S01_Opaque_Model: the NiLODNode and its shapes
+		bool transparent{};
+		std::vector<NifLod> lods;
+	};
+
+	/**
+	 * The layout LU Toolbox exports (setup_lod_data) and the game's own brick models (res/BrickModels/ndmade) have:
+	 * the root node, an NiLODNode per group with NiRangeLODData holding each level's distances, a node per level and
+	 * the level's shapes under it, named like the group. Properties as WriteNif.
+	 */
+	std::string WriteLodNif(const std::string& rootName, const std::vector<NifLodGroup>& groups);
+
 	// PNG (8-bit RGBA)
 	std::string EncodePng(const UgcRender::Image& image);