Set initial created subscription plan status to ACTIVE_PAID

[boardend]

When hosting a new QFieldCloud instance, a default subscription plan is created. This change ensures that the status of this plan is ACTIVE_PAID, so that created users can create/use projects on that instance as expected.

This change won't affect existing QFieldCloud instances in any way.

[duke-nyuki]

Task linked: QF-3925 On public, when creating a user, set its default subscription status to "active paid"

[suricactus]

The mypy error here is because QuerySet cannot take a typing arguments, feel free to fix it (I had to fix it for one of my branches I haven't pushed yet too). The other error in core... I don't know, let's retrigger the checks.

[boardend]

@suricactus thanks for looking into this

Just did a test with a new postgres_data volume, executed the migrations and created an admin via the CLI. When then creating a new user via the admin, the user as a "Active Paid" billing subscription by default 👍