"Repository name" field and "slug preview" don't have correct validation and become inconsistent when unsupported characters are entered

Steps to reproduce:

1. Open Unity Hub
2. Click "+ New project"
3. In the "Source control provider" select "GitHub" or "GitLab"
4. In the "Repository name" enter a valid name, like "test" (or use the one already there)
5. Add "+" symbols after the name
6. Observe the "Slug preview" does not contain the symbols
7. Enter any valid character, such as a letter or number
8. Observe both fields refresh and remove unsupported symbols
9. Repeat 5th step 
10. Create the project
11. Observe the repository name

Actual results: Unsupported characters are not validated immediately, unlike other fields such as Project name. They are only removed after a subsequent valid character is entered; if the project is created before that refresh, GitHub removes the characters automatically, while GitLab fails creation and shows a provider error.

Expected results: Unsupported characters should be handled consistently with other fields, either by showing immediate validation feedback or by being removed as soon as they are entered

Reproducible with versions: 3.17.2

Tested on (OS): Ubuntu 24.04

Notes:

• GitHub and GitLab have different outcomes, GitHub handles it automatically while GitLab shows error (after further testing could not reproduce this error again): 

  "Failed to create GitLab repository. project_namespace.path: can only include non-accented letters, digits, '_', '-' and '.'. It must not start with '-', '_', or '.', nor end with '-', '.', '.git', or '.atom'.; path: can only include non-accented letters, digits, '_', '-' and '.'. It must not start with '-', '_', or '.', nor end with '-', '.', '.git', or '.atom'."