Stop the prose preset from styling inline emoji

The previous fix kept the emoji <img> on the same line as the
surrounding text, but inside a prose container the typography
preset still applied its image rules — most visibly a 2 em
top/bottom margin and an enforced display — which pulled the
emoji above the baseline of the run.  Bios on the account list
and profile page, and post bodies that carried an emoji in the
middle of a sentence, all rendered with the emoji floating
above the line.

Tag the emoji <img> with the not-prose class and add an inline
"margin: 0" so the prose preset leaves it alone.  In
non-prose contexts (display names in headings) the extra class
has no effect, so the inline-block + vertical-align tuning from
the previous commit still works there.

Assisted-by: Claude Code:claude-opus-4-7

Author: dahlia

src/custom-emoji.ts

@@ -35,7 +35,7 @@ export function renderCustomEmojis(
     return input.replaceAll(CUSTOM_EMOJI_REGEXP, (match) => {
       const emoji = emojis[match] ?? emojis[match.replace(/^:|:$/g, "")];
       if (emoji == null) return match;
-      return `<img src="${emoji}" alt="${match}" style="display: inline-block; height: 1em; vertical-align: -0.125em">`;
+      return `<img src="${emoji}" alt="${match}" class="not-prose" style="display: inline-block; height: 1em; margin: 0; vertical-align: -0.125em">`;
     });
   }
 }