docs(assets): refine favicon and icon proportions for readability

[AndresSaa]

What and why

Update repository favicon and icon assets with refined SVG proportions for improved readability and sharpness at lower resolutions across all formats (wal-icon.svg, wal-icon.png, favicon.ico, favicon.png, apple-touch-icon.png, and favicon-*.png).

Testing

Validated formatting, linting, and package sanity:

• npm run lint passed with 0 errors
• npm test passed (69/69 tests)
• npm run lint:package passed (publint + attw + smoke tests)

Checklist

• PR title is a valid Conventional Commit (it becomes the squash commit on main)
• CI is green on the full Node × OS matrix
• Any new durability claim has a test in this PR (see AGENTS.md → contract invariants)
• User-visible changes update CHANGELOG.md ([Unreleased])
• No AI attribution anywhere in commits, this PR body, or code comments