Feature: Add graphical assets and project branding

[mikhailovdv]

Description

Currently, Calaf lacks visual identity and branding assets. The project requires a comprehensive set of graphical assets, including logos, icons, and other visual elements, to enhance recognizability and professional appearance across various platforms (NuGet, GitHub, and documentation).

Acceptance Criteria

Asset Creation:

• Design and create a main project logo in both .svg (vector) and .png (raster) formats
• Create NuGet package icon (64x64px minimum, .png format as per NuGet requirements)
• Create favicon for potential web documentation (16x16, 32x32, 48x48px)
• *Ensure all assets follow consistent visual style and branding

Integration Requirements:

• NuGet package correctly displays the project logo icon
• Logo is properly referenced in .csproj/.fsproj files via property
• Assets are stored in the dedicated assets/ or images/ directory in the repository root
• README.md displays the project logo at the top

Technical Specifications:

• Primary logo: .svg format for scalability
• NuGet icon: .png format, minimum 64x64px, maximum 1MB file size
  <* All assets optimized for file size without quality loss
• Assets follow accessibility guidelines (sufficient contrast, readable at small sizes)

Documentation:

• Add asset usage guidelines to the repository
• Document asset file naming conventions
• Include license information for any design elements

Additional Considerations

• Consider creating different logo variants (horizontal, vertical, icon-only)
• Ensure logo works well on both light and dark backgrounds
• Assets should be professionally designed and represent the project's purpose (calendar versioning)