fix: restrict repay asset selection with zero-LTV collateral

[vickyshaw29]

General Changes

• Restricts repay with aTokens and repay with collateral when user has zero-LTV assets enabled as collateral
• Prevents LtvValidationFailed contract revert by blocking collateral-modifying repay paths at the UI level
• Wallet balance repay remains unaffected

Closes #2873

Developer Notes

• New RepayError.tsx hook follows the existing WithdrawError.tsx pattern
• RepayModal.tsx blocks the collateral repay tab (ParaSwap swap path) and shows a warning banner
• RepayModalContent.tsx blocks the aToken repay path and disables the submit button via blocked prop
• RepayTypeSelector.tsx adds collateralDisabled prop and a null guard on MUI ToggleButtonGroup onChange
• Uses existing useZeroLTVBlockingWithdraw hook which already handles e-mode edge cases
• Enum value 0 handled with !== undefined check to avoid JS falsy trap

Reviewer Checklist

• End-to-end tests passing
• No significant bundle size increase
• 3rd party packages vetted
• Env vars added to .env.example
• No CI changes

[vercel]

@vickyshaw29 is attempting to deploy a commit to the Aave Team on Vercel.

A member of the Team first needs to authorize it.