Admin-Controlled Resource Assignment

### Epic

https://github.com/flowforge/flowforge/issues/2167

### Description

As a FlowForge Admin,
I want to have an option in the admin panel to assign specific resources to specific teams,
So that there is no need for specific FlowForge Customers / Teams to set up payment information.

### Which customers would this be available to

Licensed Edition (EE)

### Acceptance Criteria

- [ ] The Admin should have the ability to disable billing for specific Teams.
- [ ] The Admin should be able to assign fixed resources (Instances / Devices) to a Team.
- [ ] The Team Tier can only be changed by an Admin.
- [ ] If a user tries to upgrade or downgrade the tier, an Info box should appear, informing them to raise a support ticket or contact their FlowFuse contact person.
- [ ] All billing actions will be handled by Sales directly via Stripe. Sales can open a change request for customers with contracts, such as yearly billing for specific resources.
- [ ] All price tags should not be displayed for this specific team.

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate
```[tasklist]
### Tasks
- [ ] https://github.com/FlowFuse/CloudProject/issues/248
```

Start with the linked epic at FlowForge issue #2167 and the CloudProject task #248; this issue does not name files, tests, or an implementation entry point. Review the admin-panel, team-tier, fixed-resource, and billing acceptance criteria there, and consider the work done only when all listed behaviors are implemented and verified.

Written by the indexing model from the issue text.