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>

package.json

@@ -49,7 +49,6 @@
     "@tanstack/react-query": "5.100.13",
     "@tanstack/react-query-devtools": "5.100.13",
     "@tanstack/react-virtual": "3.13.25",
-    "@types/dompurify": "3.2.0",
     "@workadventure/noise-suppression": "0.0.4",
     "await-to-js": "3.0.0",
     "badwords-list": "2.0.1-4",
@@ -61,7 +60,6 @@
     "dayjs": "1.11.20",
     "deepfilternet3-noise-filter": "1.2.1",
     "domhandler": "6.0.1",
-    "dompurify": "3.4.5",
     "emojibase": "17.0.0",
     "emojibase-data": "17.0.0",
     "file-saver": "2.0.5",
@@ -100,7 +98,8 @@
     "slate-history": "0.113.1",
     "slate-react": "0.124.2",
     "styled-components": "6.4.2",
-    "ua-parser-js": "2.0.10"
+    "ua-parser-js": "2.0.10",
+    "workbox-precaching": "7.4.1"
   },
   "devDependencies": {
     "@lotusguild/element-call-embedded": "0.20.1-lotus.1",