perf(audit): emojibase lazy-split, SW precache, Prism subset, lazy images

- emojibase (~965 KB) is now fully lazy: plugins/emoji.ts loads compact data +
  shortcode maps via a memoized dynamic import (rejections reset the memo so a
  mid-deploy chunk 404 can retry); reaction labels degrade to the raw glyph
  until loaded. Consumers get FRESH array references on load (the module arrays
  populate in place — same-ref state updates would skip re-render and leave
  emoji search empty; reviewer-caught). Verified out of the eager graph.
- Service worker precaches hashed assets (workbox precacheAndRoute, 82 entries
  ~10.8 MB incl. the crypto wasm): repeat visits stop re-downloading the app.
  index.html is NOT precached — navigations stay network-first so deploys are
  picked up immediately; the media-auth fetch handler is untouched.
- ReactPrism: curated 21-language set — chunk 574 KB → 71 KB.
- Timeline inline images get loading="lazy".
- Removed dead dompurify (+types); sanitize-html is the real sanitizer.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/components/emoji-board/EmojiBoard.tsx

@@ -8,6 +8,7 @@ import React, {
   useEffect,
   useMemo,
   useRef,
+  useState,
 } from 'react';
 import { Box, config, Icons, Scroll } from 'folds';
 import FocusTrap from 'focus-trap-react';
@@ -15,7 +16,7 @@ import { isKeyHotkey } from 'is-hotkey';
 import { Room } from 'matrix-js-sdk';
 import { atom, PrimitiveAtom, useAtom, useSetAtom } from 'jotai';
 import { useVirtualizer } from '@tanstack/react-virtual';
-import { IEmoji, emojiGroups, emojis } from '../../plugins/emoji';
+import { EmojiData, IEmoji, emojiGroups, emojis, loadEmojiData } from '../../plugins/emoji';
 import { useEmojiGroupLabels } from './useEmojiGroupLabels';
 import { useEmojiGroupIcons } from './useEmojiGroupIcons';
 import { preventScrollWithArrowKey, stopPropagation } from '../../utils/keyboard';
@@ -56,6 +57,33 @@ import { VirtualTile } from '../virtualizer';
 const RECENT_GROUP_ID = 'recent_group';
 const SEARCH_GROUP_ID = 'search_group';
 
+/**
+ * Lazily pull in the emojibase data (see plugins/emoji `loadEmojiData`). The
+ * `emojis`/`emojiGroups` arrays are populated in place once the promise
+ * resolves; we wrap them in a fresh object on load so React re-renders and the
+ * board fills in. Before that, both are empty and the board shows only custom
+ * image packs / recents (which is fleeting — the load starts on mount).
+ */
+const useEmojiData = (): EmojiData => {
+  const [data, setData] = useState<EmojiData>(() => ({ emojis, emojiGroups }));
+  useEffect(() => {
+    let alive = true;
+    loadEmojiData()
+      // Fresh array references (not just a fresh wrapper): downstream memos
+      // depend on the arrays themselves, which are populated IN PLACE — same
+      // refs would skip recompute and leave emoji search empty until remount.
+      .then((loaded) => {
+        if (alive)
+          setData({ emojis: loaded.emojis.slice(), emojiGroups: loaded.emojiGroups.slice() });
+      })
+      .catch(() => undefined);
+    return () => {
+      alive = false;
+    };
+  }, []);
+  return data;
+};
+
 type EmojiGroupItem = {
   id: string;
   name: string;
@@ -75,6 +103,7 @@ const useGroups = (
 
   const recentEmojis = useRecentEmoji(mx, 21);
   const labels = useEmojiGroupLabels();
+  const { emojiGroups: loadedEmojiGroups } = useEmojiData();
 
   const emojiGroupItems = useMemo(() => {
     const g: EmojiGroupItem[] = [];
@@ -99,7 +128,7 @@ const useGroups = (
       });
     });
 
-    emojiGroups.forEach((group) => {
+    loadedEmojiGroups.forEach((group) => {
       g.push({
         id: group.id,
         name: labels[group.id],
@@ -108,7 +137,7 @@ const useGroups = (
     });
 
     return g;
-  }, [mx, recentEmojis, labels, imagePacks, tab]);
+  }, [mx, recentEmojis, labels, imagePacks, tab, loadedEmojiGroups]);
 
   const stickerGroupItems = useMemo(() => {
     const g: StickerGroupItem[] = [];
@@ -177,6 +206,7 @@ function EmojiSidebar({ activeGroupAtom, packs, onScrollToGroup }: EmojiSidebarP
   const usage = ImageUsage.Emoticon;
   const labels = useEmojiGroupLabels();
   const icons = useEmojiGroupIcons();
+  const { emojiGroups: loadedEmojiGroups } = useEmojiData();
 
   const packLabels = useMemo(() => {
     const map = new Map<string, string | undefined>();
@@ -234,7 +264,7 @@ function EmojiSidebar({ activeGroupAtom, packs, onScrollToGroup }: EmojiSidebarP
         }}
       >
         <SidebarDivider />
-        {emojiGroups.map((group) => (
+        {loadedEmojiGroups.map((group) => (
           <GroupIcon
             key={group.id}
             active={activeGroupId === group.id}
@@ -409,13 +439,14 @@ export function EmojiBoard({
   const [emojiGroupItems, stickerGroupItems] = useGroups(tab, imagePacks);
   const groups = emojiTab ? emojiGroupItems : stickerGroupItems;
   const renderItem = useItemRenderer(tab);
+  const { emojis: loadedEmojis } = useEmojiData();
 
   const searchList = useMemo(() => {
     let list: Array<PackImageReader | IEmoji> = [];
     list = list.concat(imagePacks.flatMap((pack) => pack.getImages(usage)));
-    if (emojiTab) list = list.concat(emojis);
+    if (emojiTab) list = list.concat(loadedEmojis);
     return list;
-  }, [emojiTab, usage, imagePacks]);
+  }, [emojiTab, usage, imagePacks, loadedEmojis]);
 
   const [result, search, resetSearch] = useAsyncSearch(
     searchList,