docs: improve rbac and permissions readability

[Holmus]

Thanks for submitting a PR! Please check the boxes below:

• I have added information to docs/ if required so people know about the feature!
• I have filled in the "Changes" section below?
• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

Changes

• Restructured RBAC docs with clearer explanations of permission levels (organisation/project/environment) and role types
• Added practical examples for common permission setups (developers with production restrictions, QA read-only access, etc.)
• Updated change requests docs with a permissions table for create/approve/publish actions
• Added permissions section to data model docs explaining how permissions align with the data hierarchy

How did you test this code?

Ran docs locally, verified SVGs look good, that links work, that the text makes sense and that the general order concepts are presented in makes sense.

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Project	Deployment	Review	Updated (UTC)
docs	Ready	Preview, Comment	Jan 5, 2026 10:58am

2 Skipped Deployments

Project	Deployment	Review	Updated (UTC)
flagsmith-frontend-preview	Ignored	Preview	Jan 5, 2026 10:58am
flagsmith-frontend-staging	Ignored	Preview	Jan 5, 2026 10:58am

[khvn26]

Kindly check the linting failure:

  [cause]: Error: Docusaurus found broken links!
  
  Please check the pages of your site in the list below, and make sure you don't reference any path that does not exist.
  Note: it's possible to ignore broken links with the 'onBrokenLinks' Docusaurus configuration, and let the build pass.
  
  Exhaustive list of all broken links found:
  - Broken link on source page path = /administration-and-security/access-control/rbac:
     -> linking to /project-management/tags

[matthewelwell]

On the whole, this seems like a great improvement. I've added a few minor suggestions and one question, but nothing that is strictly necessary I don't think.