Build invoice duplicate/clone UI with pre-fill, field validation, conflict detection, and optimistic feedback

[Kingsman-99]

Description

Build a full duplicate/clone flow for invoices: a Duplicate button on the detail page, navigation to a pre-filled create form, field-level validation showing what changed vs the original, detection of conflicting deadlines, and optimistic UI feedback while the clone transaction is in-flight.

Acceptance Criteria

• A Duplicate button appears on /invoice/[id] only for the invoice creator (hide for all other wallets)
• Clicking opens a modal asking for a new deadline before navigating — do not navigate with stale deadline
• On confirm, navigates to /invoice/new with all original fields pre-populated via URL state or query params (recipients, amounts, token, options)
• Create form shows a Cloned from #ID banner linking back to the original
• Fields that differ from the original are highlighted with a yellow border and tooltip "Changed from original"
• If the new deadline is before now + 1 hour, form shows inline error "Deadline must be at least 1 hour in the future" and blocks submission
• On submit, calls cloneInvoice SDK method; button shows spinner and "Cloning..." text during submission
• On success, shows toast "Invoice #NEW_ID created" and navigates to /invoice/NEW_ID
• On failure, shows error toast with the contract error message and keeps form state intact
• Unit test for the deadline validation logic; integration test for the pre-fill URL parsing

Context

• Invoice detail page: src/app/invoice/[id]/page.tsx
• Invoice create form: src/app/invoice/new/page.tsx
• SDK cloneInvoice from split-sdk issue Build invoice push notifications #6

[Smartdevs17]

Can I work on this?