Restore corrected EmberHarmony asset variants

[sydneyrenee]

Summary

• restore the main-branch identity PNG for packages/identity/mark-512x512.png
• restore the transparent-block mark-light.svg from main
• restore docs favicon.svg and favicon-v3.svg to the original 24x24 transparent SVG contract

Verification

• git diff --check
• xmllint --noout packages/identity/mark-light.svg packages/docs/favicon.svg packages/docs/favicon-v3.svg
• compared restored files byte-for-byte against origin/main

[gemini-code-assist]

Code Review

This pull request simplifies several SVG assets, including favicons and identity marks, by replacing complex paths with grid-like rect elements. However, the reviewer correctly identified that all the newly added rect elements contain empty fill="" attributes. Since empty fill attributes are invalid in SVG, they can cause rendering failures or default to black. The reviewer suggested replacing these with valid color values, such as currentColor or specific hex codes, to ensure proper rendering.