Add stream deposit (top-up) UI for existing streams

[pragmaticAweds]

Context

The PaymentStreamClient.deposit() method exists in the SDK (line ~42-44) allowing stream senders to add more tokens to an existing stream. However, there is no UI for this action. If a sender creates a stream and later wants to extend the payment by depositing more tokens, they have no way to do it through the frontend.

What Success Looks Like

• Active streams show a "Deposit" or "Top Up" action in the stream actions menu (visible only to the sender)
• Clicking it opens a modal/form with an amount input and the current stream balance displayed
• Submitting the deposit calls the SDK's deposit() method and shows transaction feedback via notify
• The stream's total amount updates after a successful deposit

Implementation Guidance

• packages/sdk/src/PaymentStreamClient.ts — the deposit() method
• apps/web/src/components/modules/payment-stream/StreamActionsCell.tsx — where to add the new action
• Follow the pattern of existing stream actions (cancel, withdraw) for the transaction flow
• The modal should show: current stream balance, remaining amount, and an input for the top-up amount
• Validate that the deposit amount doesn't exceed the user's token balance
• Use apps/web/src/utils/amount-validation.ts for amount input validation

[PrettyClarra]

@PrettyClarra has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hey Champ, Can i get on this and get it done?

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[drips-wave]

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