chore: UI fix and improvements

[keita-determined]

Description

• DET-7394
• Add sign-in animation

Test Plan

• Check if new project/workspace/model button won't remain highlighted after closing modal
• Check if User settings dropdown won't remain highlighted after clicking
• Check if there is a spin after clicking sign in button

Commentary (optional)

Checklist

• [ ] User-facing API changes need the "User-facing API Change" label.
• [ ] Release notes should be added as a separate file under docs/release-notes/. See Release Note for details.
• [ ] Licenses should be included for new code which was copied and/or modified from any external code.
• [ ] If modifying /webui/react/src/shared/ verify make -C webui/react test-shared passes.

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