feat: Add custom size props to modal

[amanabiy]

Description

This PR extends the Modal component with custom dimension support by adding width and height props, building on the position prop introduced in the previous PR.

Note: The base branch is dev-v3-amanabiy-modal-top-position to isolate changes from the position prop PR for easier review.

New Features:

• width prop: Allows specifying custom modal width (minimum 320px). Takes precedence over the size prop when provided.
• height prop: Enables custom modal height with automatic content scrolling when content exceeds the specified height.

The base is made to dev-v3-amanabiy-modal-top-position so that you can review the main changes only related to this PR, and not the previous prs which adds position prop and different sizes.

Behavior:

• Both props respect viewport constraints - if specified dimensions exceed available space, the modal uses maximum available space
• When custom height is set and content overflows, the content is scrollable
• Minimum width constraint ensures that the minimum width builders can set is equal to the smallest size
• Minimum height constraint ensures content area is at least 60px for accessibility
• Proper ARIA attributes (role="region", aria-label) are applied to scrollable content regions for screen reader support

Related links, issue #, if available: gfq0AFhyrah9

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.42%. Comparing base (37685a3) to head (78a1bae).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4252   +/-   ##
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  Coverage   97.42%   97.42%           
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  Files         891      891           
  Lines       26098    26124   +26     
  Branches     9435     9455   +20     
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+ Hits        25426    25452   +26     
  Misses        629      629           
  Partials       43       43           

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[jperals]

"constrained" suggests that a maximum is applied to a given value, but here it is a minimum. Can we find a different phrasing? Is this the vertical equivalent of the minimum 320px width mentioned in the width prop above? If so, could we harmonize both descriptions?