fix: CSS typo, btoa unicode, denoise validation, title flash

[saurabhhhcodes]

Fixes #1659
Fixes #1660

Summary

• Correct the details > summary selector so disclosure summaries receive the intended styling.
• Encode shared recipe JSON before Base64 conversion and decode it symmetrically, allowing Unicode recipe text in Copy Link URLs.

Validation

• npm install --package-lock=false --legacy-peer-deps --ignore-scripts --no-audit --no-fund
• npm run build
• Direct Unicode share-link round-trip assertion
• git diff --check

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