feat: add Backspace design prototype and rebrand from Opencord

- Add Backspace-design-prototype.html: finalized "Aether Drift" design
  language with warm matte surfaces and subtle frosted glass accents
- Update CLAUDE.md with DESIGN SYSTEM section and remove Discord clone references
- Rename all Opencord references to Backspace across the full codebase
- Archive outdated design experiments and Discord-specific assets
- Add science-backed accessibility fallback (prefers-reduced-transparency)

packages/web/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "@opencord/web",
+  "name": "@backspace/web",
   "version": "1.0.0",
   "private": true,
   "type": "module",
@@ -10,7 +10,7 @@
   },
   "dependencies": {
     "@livekit/components-react": "^2.7.4",
-    "@opencord/shared": "workspace:*",
+    "@backspace/shared": "workspace:*",
     "@sapphi-red/web-noise-suppressor": "^0.3.5",
     "livekit-client": "^2.9.0",
     "prism-react-renderer": "^2.4.1",