fix: add 'customise avatar later' tip & update buttons animations

[RominaMarchetti]

What does this PR change?

This PR adds a hint, when creating a new account, to warn users that the avatar can be customize later if they don't find one that represents them.
Besides, avatar actions buttons textures have been update so please validate nothing odd happens while interacting with them.

Test Steps

1. Create a new account
2. Check that bellow the avatar buttons to undo/redo/randomize the hint appears.

3. Look into the undo/redo/randomize. Validate textures look crisp and animations normal.

[github-actions]

Windows and Mac build successful in Unity Cloud! You can find a link to the downloadable artifact below.

Name	Link
Commit	621d72d
Logs	https://github.com/decentraland/unity-explorer/actions/runs/23651146885
Download Windows	https://github.com/decentraland/unity-explorer/suites/62318796544/artifacts/6146367164
Download Windows S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/fix/add-customise-avatar-later-tip-&-update-buttons-animations/pr-20340-621d72d/Decentraland_windows64.zip
Download Mac	https://github.com/decentraland/unity-explorer/suites/62318796544/artifacts/6146255094
Download Mac S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/fix/add-customise-avatar-later-tip-&-update-buttons-animations/pr-20340-621d72d/Decentraland_macos.zip
Built on	2026-03-27T15:03:34Z

[DafGreco]

✔️ PR reviewed and approved by QA on both platforms following instructions playing both happy and un-happy path

Regressions for this ticket had been performed in order to verify that the normal flow is working as expected:

• [✔️ ] On boarding with new account
• [✔️] Log In/Log Out
• [✔️ ] Backpack and wearables in world
• [✔️ ] Emotes in world and in backpack
• [✔️ ] Teleport with map/coordinates/Jump In
• [ ✔️] Chat and multiplayer
• [✔️ ] Profile card

Evidence:

20260327-1404-52.7018783.mp4

More evidence on the following link