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/UgcBricks.h

@@ -64,7 +64,12 @@ namespace UgcBricks {
 		Material GetMaterial(uint32_t id) const;
 
 		// Every geometry file of a design, in order (.g, .g1, ...); empty when the design has none. Loaded once.
-		std::shared_ptr<const std::vector<Geometry>> GetDesign(uint32_t design);
+		// `lod`: the brickprimitives level, the library's own when omitted; a design without that level uses the
+		// next more detailed one.
+		std::shared_ptr<const std::vector<Geometry>> GetDesign(uint32_t design, std::optional<uint32_t> lod = std::nullopt);
+
+		// Designs loaded (for the memory report)
+		size_t CachedDesigns() const;
 
 		const std::filesystem::path& GetResPath() const { return m_Res; }
 
@@ -72,7 +77,7 @@ namespace UgcBricks {
 		std::filesystem::path m_Res;
 		uint32_t m_Lod;
 		std::map<uint32_t, Material> m_Materials;
-		std::mutex m_Mutex;
-		std::map<uint32_t, std::shared_ptr<const std::vector<Geometry>>> m_Designs;
+		mutable std::mutex m_Mutex;
+		std::map<uint64_t, std::shared_ptr<const std::vector<Geometry>>> m_Designs; // lod << 32 | design
 	};
 }