B-tree-visualizer Build 12

Add comprehensive B-tree animation system with embedded font

- Implemented animated key insertion with smooth movement and positioning
- Added node split animations with violation indicators (TOO MANY KEYS)
- Implemented deletion animations with highlight and fade-out effects
- Fixed duplicate key prevention using tree.contains() checks
- Replaced rand() with std::mt19937 for proper randomization
- Embedded JetBrains Mono font into binary using CMake custom command
- Fixed zoom-to-fit vertical alignment (proper Y calculation)
- Delayed zoom until after animations complete
- Organized CMake scripts into dedicated cmake/ directory
- Updated .gitignore to exclude build artifacts and generated headers