Optional end-user link in left panel to point to customer's internal documentation

Is your feature request related to a problem? Please describe.
- To get to our company documentation on how to request and use Harbor Registry, 5000 users have to bookmark a web site. Most call support team which is overwhelmed.
- To access our docs in gpt model, we have to distribute a file to 5000 users that adds a chrome extension.

Describe the solution you'd like
- Add a option for admins set an http link to company Harbor docs. Even multiple optional links may be helpful, e.g., for announcements of releases and maintenance downtime. Or link to TEAMS or Slack.
- Add an optional Icon that links to an AI model containing announcements and documentation

Describe the main design/architecture of your solution
- Left panel links should be configurable on system admin page and appear on all UI pages.
- AI model link should be configurable on system admin page or AI icon should float on all pages.

Describe the development plan you've considered
- None

The issue names no files, tests, or entry points. Start by locating the system admin page and left-panel UI configuration entry points, then clarify whether external documentation, announcement, chat, and AI links are all required. Done should include an agreed configuration design and links appearing consistently across UI pages.

Written by the indexing model from the issue text.