fix(ui): make limits clearer in create repo form (#7402)

Resolves: #7341

Previously, the Create Repository button was only enabled if a user was able to create a repo in their own namespace. However, if they had reached the global repo limit, but were stlll able to create a repo in an org, the button would still be disabled.

In this pull request, the create repo form now:

1. Behaves like it always did previously if the user has not reached the repo limit.

2. If the User has reached the repo limit, and they are unable to create a repo in any of their orgs (or they have no orgs), the create repo form is displayed as:
![Screenshot](/attachments/9f22f43d-0036-4c48-b794-54302c0f241c)

3. If the User has reached the repo limit, and the **limit is greater than zero**, an alert appears at the top of the form, and they are only allowed to choose from the orgs that they are allowed to create repos in:
![Screenshot](/attachments/f5508e05-74fd-4858-9e95-967bd7017abd)

4. If the User has reached the repo limit, and the **limit is equal to zero**, no alert is displayed, as no user can create repos on that instance, and they are only allowed to choose from the orgs that they are allowed to create repos in:
![localhost_3000_repo_create (4).png](/attachments/e7a87da8-c19c-47e1-845e-2afc3667ab02)

Co-authored-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7402
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Ryan Lerch <rlerch@redhat.com>
Co-committed-by: Ryan Lerch <rlerch@redhat.com>

models/fixtures/user.yml

@@ -93,7 +93,7 @@
   login_name: org3
   type: 1
   salt: ZogKvWdyEx
-  max_repo_creation: -1
+  max_repo_creation: 1000
   is_active: false
   is_admin: false
   is_restricted: false