Add help doc: How to create an aging report on the Spend page

[MelvinBot]

Description

Create a help doc article explaining what an "aging report" is and how to create one using Expensify's Spend page search operators.

Context

Users need guidance on how to use the Spend page to build aging reports — views that show how long expenses (e.g., unapproved Expensify Card transactions) have been outstanding, broken down by time period (month, quarter, etc.). The existing search operators (group-by:month, group-by:quarter, status:, expense-type:, date filters) already support this, but there's no dedicated help article explaining the concept or walking users through it.

Slack thread: https://expensify.slack.com/archives/C03U7DCU4/p1777945853807759

Proposed Location

App/docs/articles/new-expensify/reports-and-expenses/Create-an-Aging-Report.md

Key Content

• What an aging report is and why it's useful (e.g., tracking unapproved card accruals over time)
• Step-by-step instructions using search operators on the Spend page
• Example queries using group-by:month, group-by:quarter, date ranges, status:outstanding, expense-type:card
• How to save searches for quick re-use
• How to visualize results with view:bar or view:line

A draft PR with proposed content will follow.