refactor: upgrade prism-react-renderer from v1 to v2

[pettinarip]

Summary

Upgrades prism-react-renderer from v1 (1.1.0) to v2 (2.4.1). Deferred from #17781.

• Use v2 named exports (Highlight, Prism, themes) — drop defaultProps
• Replace custom theme objects with built-in themes.duotoneLight / themes.duotoneDark
• Fix SSR hydration mismatch: use useTheme() directly instead of useColorModeValue (which defaulted to dark on first render)
• Transparent backgroundColor on both themes so bg-background-highlight controls the background
• overflow-scroll → overflow-auto (scrollbars only when needed)
• Type getValidChildrenForCodeblock param, use bare catch

Test plan

• Code blocks render correctly in light and dark mode
• Theme toggle doesn't flash or mismatch
• Solidity, JS, Python, Bash syntax highlighting works
• Copy-to-clipboard and collapse/expand unchanged
• No horizontal scrollbar when code fits

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[wackerow]

@pettinarip nice! Overall looks good, all above "tests" look good, but just noting a couple things:

(JavaScript example)

Production:

PR:

1. We're getting an extra blank line at the ends
2. Copy button has lost our primary color
3. Contrast has dropped a bit with this new color scheme
4. Dark mode web3.eth.getBlockNumber().then(console.log) doesn't really show any distinction between tokens

I would consider first two as blockers. The others seem fine, just noting the difference.

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Separately, this has made me realize that there are a lot of code fences that have their own empty lines (unrelated to above bug) at the end that we could easily regex and clean up (out of scope here)

[wackerow]

Lgtm! Thanks @pettinarip