docs: update Otto the otter mascot logo

[petercrocker]

Summary

Replaces the Otto mascot image shown on the FAQ page with the new flat-style blue otter logo.

Changes

• Replaced docs/docs/media/otto.png with the updated logo

Test Plan

• Visit the FAQ page locally and confirm the new Otto image renders correctly under "What is the name of the otter?"

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Supersedes #9148, which was inadvertently branched off the docs-revamp branch and ended up carrying 60 files. This branch is rebased on stable so the diff is just the single PNG swap.

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Summary by cubic

Updates the Otto mascot on the docs FAQ to the new flat-style blue logo for brand consistency. Replaces docs/docs/media/otto.png so the “What is the name of the otter?” section shows the new image.

^{Written for commit 0c9c31c. Summary will update on new commits.}