Restore `GalleryAdd()` and `GalleryEdit()` in `media-views.js` to ensure back-compat.

See [27362].


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Theme installer keyboard fixes. Updates [28033] and [28036].

props matveb.
see #27521.

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Escape playlist data in templates.

props wonderboymusic.
fixes #27710.

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Don't show featured images for image attachments. Remove abstractions for now.

fixes #27673.

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3.9 about page text, rough cut.

props markjaquith, nacin.
see #27713.

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Harden HMAC verification. props duck_.

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3.9-RC1

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