Showcase ModelForge with a visual README

[michaelbawuah]

Overview

• Rework the repository landing page into a concise product overview with a branded header, release-flow graphic, and console illustration.
• Preserve the detailed technical content in docs/engineering-guide.md, with working links to the existing documentation.
• Identify the UI image as illustrative example data and state that AWS public hosting has not been launched.

Verification

• GitHub CI run #182 passed: Python tests and lint, Go tests and vet, Terraform validation, container builds, and live Compose smoke.
• Rendered and inspected all three SVG assets locally.
• Parsed SVG XML, checked every local link in both README files, and ran git diff --check.