Add payment method preference memory per recipient

[Kingsman-99]

Description

PaymentMethodSelector.tsx presumably asks for payment method/token choice every time with no memory of a payer's prior preference for a given recipient. This issue adds per-recipient preference memory.

Technical Context

Involves src/components/PaymentMethodSelector.tsx. Store the last-used token/method per (payer, recipient) pair in localStorage; pre-select it as the default on subsequent payments to the same recipient, while still allowing override.

Acceptance Criteria

• First payment to a new recipient has no pre-selected preference (current default behavior unchanged)
• Subsequent payments to the same recipient pre-select the previously used method/token
• Explicitly choosing a different method on a later payment updates the stored preference
• Preference storage is scoped per connected address (switching wallets doesn't leak another wallet's preferences)
• Unit tests: first-time no-preference behavior, preference update on override, per-address scoping

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