feat: Introduce TextureAtlas for efficient texture management

- Added TextureAtlas class to manage multiple textures packed into a single large texture, improving rendering performance and reducing GPU state changes.
- Implemented methods for allocating regions, packing bitmaps, and drawing regions from the atlas.
- Removed the DrawDungeonTabView function from DungeonCanvasViewer as it is no longer needed with the new EditorCard system.
- Updated CMake configuration to include texture_atlas.cc in the build process.
- Refactored Room class to eliminate dependency on Arena graphics sheets, transitioning to per-room graphics for rendering.

src/app/editor/dungeon/dungeon_canvas_viewer.cc

@@ -12,8 +12,6 @@
 
 namespace yaze::editor {
 
-using ImGui::Separator;
-
 // DrawDungeonTabView() removed - DungeonEditorV2 uses EditorCard system for flexible docking
 
 void DungeonCanvasViewer::Draw(int room_id) {