feat: Add Default lang to web app UI

[SergeWilfried]

Feature Description

As a user I would like to change the platform language from my account.

Use Case

No response

Proposed Solution

No response

Alternatives (optional)

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Additional Context

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Please check the boxes that apply to this feature request.

• [X] I have searched the existing feature requests to make sure this is not a duplicate.
• [X] I have provided a detailed description of the requested feature.
• [X] I have explained the use case or scenario for this feature.
• [X] I have included any relevant technical details or design suggestions.
• [X] I understand that this is a suggestion and that there is no guarantee of implementation.

[github-actions[bot]]

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@SergeWilfried has 6 open issues assigned already. Consider whether this issue should be assigned to them or left open for another contributor.