Add Guardian operator profiles and selection guidance

## Problem

Users are asked to choose a Guardian operator without enough information to make an informed decision.

The Guardian cards do not clearly explain:

- Guardian operator background
- what they do
- what information the operator can and cannot access;
- whether factors such as region, availability, or performance matter.

As a result, users may choose the default operator or select one based only on name recognition.

## Proposed improvement

Provide Guardian operator information through two entry points:

- a card in the onboarding flow
- an entry in Settings for existing users.

Each Guardian card should provide access to verified information about the operator, its role, data-access boundaries, region, and current availability. Explain that the Guardian can be changed later.

## Expected result

Users can understand and compare the available Guardian operators before selecting one.

## Related

- #479
- #455
- #464
- PR #508
- PR #786

The issue mentions adding operator profiles and selection guidance in the onboarding flow and Settings. Look for the onboarding component files and settings UI components. Related issues #479, #455, #464 and PRs #508, #786 provide context on Guardian operators and UI changes. Start by understanding the current operator selection logic and the data model for operators. 'Done' means users can view verified operator information and compare them before selection.

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