feat: Allow AVIF content type in PhotoCache

[Peque]

• Resolves: Feature request: Support AVIF format in PhotoCache #49980

Summary

AVIF is the only well-supported commonly used format for still images that is missing in CardDAV's PhotoCache (excluding SVG for security concerns).

This patch would be required in order to be able to use AVIF in contact photos.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• (N/A) Tests (unit, integration, api and/or acceptance) are included
• (N/A) Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[Peque]

@st3iny I guess this would also require a follow-up update in Contacts (like it did for WebP support). 😊

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