fix(web): stabilize player album art sizing

[pollychen-lab]

What does this change intend to accomplish?

Closes #1103.

This keeps the player page metadata column stable when album art is missing or fails to load by reserving a square album-art area in CSS. The player metadata width now comes from a reusable class instead of the prior inline style, and the album art scales within the reserved area with a 98vw cap for narrow mobile screens.

Validation

• npm run build from web/
• npx eslint src/pages/Player/Player.jsx from web/ (currently fails on existing formatting in Player.jsx: semicolons, indentation, and quote style outside this CSS sizing change)

Checklist

• Have you tested your changes and ensured they work?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• If applicable, have you updated the documentation/manual?
• If applicable, have you updated the CHANGELOG?
• Does your submission pass linting & tests? You can test on localhost using ./scripts/test
• Have you written new tests for your core features/changes, as applicable?
• If this is a UI change, have you tested it across multiple browser platforms on both desktop and mobile?