Refresh foundryR hex sticker

[farach]

Summary

• Replace the package hex sticker with a Swiss-minimal composition: open field, single geometric forge/diamond mark, restrained Azure-blue palette, and no tagline overflow.
• Regenerate pkgdown favicon SVG and PNG variants from the simplified icon source.
• Avoid embedding Microsoft trademark artwork in the public repo; private rollout assets are being handled separately.

Validation

• Parsed updated SVG files as XML.
• Regenerated favicon PNGs at 96, 180, 192, and 512 px.
• Ran devtools::test(): 0 failures, existing environment warning only.