[Frontend] Implement avatar upload in settings (currently coming soon)

[grantfox-oss]

Telegram (ask questions / claim the issue here first): https://t.me/+DOylgFv1jyJlNzM0

Why this matters

src/app/[locale]/settings/page.tsx shows Avatars are not supported yet, coming soon. Profile identity matters for a social, gamified product. This is a self-contained feature a contributor can own end to end.

Acceptance criteria

• Allow selecting and previewing an image with client side validation (type, size, dimensions)
• Upload through the backend (or chosen storage) and persist the avatar URL on the user
• Show the avatar wherever the user is represented and provide a remove action
• Accessible file input with progress and error states

Files to touch

• src/app/[locale]/settings/page.tsx
• src/app/stores/useUserStore.ts
• src/app/hooks/useApi.ts

Out of scope

• Image moderation
• Cropping editor (can be a follow-up)

[Peolite001]

I would love to work on this issue

[grantfox-oss]

🦊 GrantFox — @Peolite001 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #13)
2. Your PR will be reviewed by the LabsCrypt maintainers

Good luck! Track your progress on GrantFox.