[Design]: improve call attendee thumbnail background

[Antreesy]

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Feature request

Describe the solution you'd like

• Derive blurhash from the person avatar
• In case of missing avatar - lighten background

Current	Proposal

Describe alternatives you've considered

• CSS filter blur (less-performant)

[jancborchardt]

FYI @nimishavijay something I proposed to @Antreesy and @DorraJaouad as it seems relatively small effort high impact improvement to move from an overly colorful voice call view to one that is more relevant (with blurred avatar or blurhash) or more elegant (with subdued colors or dark/light transparent-ish background).