feat: italicize quotation environments

[pyramation]

Summary

Sets quoted passages in italics, so quotation reads as a quote rather than as body text with an indent. Deliberate style change — it's not restoring anything, the pre-rewrite site rendered quotes upright.

Italics are inherited, so rendered math inside a quote would be skewed on top of MathJax's own italic conventions; the rule is paired with an upright override for .math / .MathJax / mjx-container inside the quote. Verified in a browser on a quote containing inline math: blockquote.quotation italic, mjx-container normal.

Link to Devin session: https://app.devin.ai/sessions/e51e8ecb94d241bd8d89e65e642c3e43
Requested by: @pyramation

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