[Bug][SubscriptionBilling] Contract lines of type G/L Account never post to the selected G/L account

Describe the issue

For contract lines with Contract Line Type = G/L Account, the account selected on the line is never used in posting. Both the invoice posting and the deferral release always use the Subscription Billing accounts from the General Posting Setup, so the G/L account entered on the line has no effect on the resulting G/L entries.

Example: a user creates a Subscription Line with G/L account 0220 (Rent) to address that account directly. When the invoice is posted, the deferral and revenue accounts from the General Posting Setup are used instead, so account 0220 is never used anywhere besides on the line itself — not even when the contract deferrals are released.

The same applies to Vendor Subscription Contract lines of type G/L Account.

Expected behavior

If a contract line has type G/L Account, the selected account should be the final result of the posting:

• Using the deferral account from the General Posting Setup for the accrual itself is fine.
• The target account from the line (e.g. 0220) should be carried into the contract deferrals, so that releasing the deferrals posts to that account instead of the generic contract account from the General Posting Setup.
• For lines that do not create deferrals, the posting should use the selected G/L account directly.

Steps to reproduce

1. Create a Customer Subscription Contract line with Contract Line Type = G/L Account and No. = 0220.
2. Create the contract invoice via Recurring Billing.
3. Open the posting preview (or post the invoice and inspect the G/L entries).
4. Actual: the posting uses the Customer Subscription Contract Deferral Account (with deferrals) or the Customer Subscription Contract Account (without deferrals) from the General Posting Setup — account 0220 is never posted to.
5. Expected: account 0220 ends up as the revenue account of the posting, either directly or via the release of the contract deferrals.

Additional context

No response

I will provide a fix for a bug

• I will provide a fix for a bug

Start with the recurring billing invoice posting flow and its handling of Customer and Vendor Subscription Contract lines of type G/L Account. Trace how the selected account and deferrals move through invoice posting and deferral release; done means account 0220 is posted directly when no deferral is created and is used when the deferral is released.