Support liability repayments instead of only editing the total liability value #7449

Problem

Currently, liabilities can only be adjusted by editing the total outstanding value.

For example:

• Initial liability: €20,000
• Monthly repayment: €300

I would like to record the monthly repayment as a transaction that automatically reduces the outstanding liability.

However, entering a negative value (e.g. -300) is not allowed because the input validation rejects it. As a result, the only way to keep the liability up to date is to manually overwrite the remaining balance each month.

This means there is no repayment history and no easy way to track how the liability has been reduced over time.

Feature Request

It would be great if Ghostfolio supported liability repayments by allowing users to:

• Record repayments against an existing liability.
• Automatically reduce the outstanding balance.
• Keep a complete repayment history.
• Optionally support recurring monthly repayments.

This would make it much easier to track loans, mortgages and other liabilities without manually editing the remaining balance every month.