Modernize TinyMongo branding

[schapman1974]

What changed

• modernizes the primary TinyMongo PNG and SVG artwork
• combines the recognizable stacked documents and Mongo-style leaf with the new dark mint/cyan visual system
• adds a standalone square mark for websites, social cards, and application icons
• preserves the exact 1.3.0-era artwork as legacy PNG and SVG files
• links the README logo and project homepage metadata to https://tinymongo.org/

Why

The new tinymongo.org design introduced a stronger visual system, but the GitHub and PyPI artwork still used the older identity. This creates one bridge design that remains recognizable while keeping the project consistent across channels.

Impact

The README keeps its existing image URL, so the refreshed asset appears without changing how the image is served. The website is now discoverable from the README, package metadata, and GitHub About panel. There are no package or runtime behavior changes.

Validation

• validated both SVG files with xmllint
• rendered and visually inspected the primary logo and standalone mark
• verified expected PNG dimensions and file types
• deployed and verified the matching mark on tinymongo.org