Add support for the financial insights transactions update CLI command

[selinafeng-stripe]

Adds support for the transactions update CLI command for updating the category/description on a transaction.

link-cli transactions update lbctxn_... --category=restaurants --description="Hawa Murray Hill"
✓ Transaction updated

  ID: lbctxn_...
  Description: Hawa Murray Hill
  Category: restaurants
  Amount: -$8.62
  Date: 2026-08-23
  Status: succeeded

Listing the transaction after shows the updated category and description:

link-cli transactions list
Transactions

 Date               Amount  Status      Category          Description
 --------------------------------------------------------------------------------------------------------------
 2026-08-23         -$8.62  succeeded   restaurants       Hawa Murray Hill

When the category is invalid:

link-cli transactions update lbctxn_... --category=abcdef --description="Hawa Murray Hill"
✗ Failed to update transaction
Failed to update transaction (400): Invalid category: abcdef

When the resource is not authorized

link-cli transactions update lbctxn_... --category=restaurants --description="Hawa"
✗ Failed to update transaction
Failed to update transaction (403): Transaction not authorized

When the transaction is not found:

link-cli transactions update lbctxn_... --category=restaurants --description="Hawa"
✗ Failed to update transaction
Failed to update transaction (404): Transaction not found