Add an admin invoice review page listing all invoices pending approval with approve and reject actions

[Chucks1093]

Summary

Platform admins have no in-app interface to review and approve seller invoices before they go live. An admin-only review page should list all invoices in the pending_review state with approve and reject buttons and an optional rejection reason input.

Scope

• Fetch all pending_review invoices from the admin endpoint on page mount
• Display each invoice with title, seller wallet (truncated), face value, and submission date
• 'Approve' button transitions the invoice to published and removes it from the list
• 'Reject' button opens an inline text input for the rejection reason before confirming
• Redirect non-admin wallets to the home page with a 'Not authorised' toast

Acceptance Criteria

• All pending review invoices listed with correct fields
• Approve removes the invoice from the list and transitions status
• Reject requires a reason before confirming
• Non-admin wallets redirected with 'Not authorised' toast
• Empty state shown when no invoices are pending review

ETA: 12 hours

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