Stake > Rewards page improvements

[0xhuman]

Is your feature request related to a problem? Please describe.
The Stake > Claim page allows users to click the 'CLAIM' button for MOBI staking rewards even if they have already claimed for that week. This results in nothing happening.

Describe the solution you'd like

• The 'Claim My Share' button should be grayed-out if a user has already claimed that week.
• Add a disclaimer that "MOBI buyback rewards can be claimed once per week"
• 'Mobi Rewards' and 'Total Mobi Distributed...' should have all caps MOBI

Thanks @ccc in our Discord for the tips