Improvements and fixes

• Updated how internal user and client user deletions work. When a user is deleted, their email is now immediately available for use again. This fixes a common problem new customers have who frequently invited themselves as a client (using another email) and then later wanted to use this same email for an internal user.
• Simplified how customers can manage their Portal subscription. Customers can now see their plan, past invoices, and manage their payment method, all on the Settings/Plans page.
• Added logic that kicks client users out of active sessions immediately after they are deleted by internal users.
• Improved the invoices page that is shown to internal users when no invoices have been created yet.
• Fixed a bug where resending a client invite didn't work in some scenarios.