BurnForm: show current token balance before burn

[Ejirowebfi]

Description

BurnForm.tsx asks for an amount to burn but does not show the user's current token balance. Users cannot tell if they are about to burn more than they hold.

Tasks

• Use useTokenBalance hook to fetch the connected wallet's balance for the selected token
• Display the balance above the amount input
• Add a "Max" button that fills the amount field with the full balance
• Validate that the burn amount does not exceed the balance

Acceptance Criteria

• Current balance is displayed before the amount input
• "Max" button populates the amount field correctly
• Submitting an amount greater than the balance shows an inline error