fix(console): Billing seat bugs

[betimshahini]

Description

• Scheduled payment with multiple products (service plan + seat) doesn't show in Invoices and payments section of the Billing page after making seat downgrades.
• When accepting invites (for pending invitees), should check for current vs expected number of seats and return server error if the numbers don't line up, similar to when a non-paid admin user is performing admin tasks.
• Copy on downgrade modal states that free plan features will be removed as part of the downgrade of a plan to Free.