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- Archive outdated design experiments and Discord-specific assets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)

pnpm-lock.yaml

@@ -26,6 +26,9 @@ importers:
 
   packages/server:
     dependencies:
+      '@backspace/shared':
+        specifier: workspace:*
+        version: link:../shared
       '@fastify/cors':
         specifier: ^9.0.1
         version: 9.0.1
@@ -41,9 +44,6 @@ importers:
       '@fastify/websocket':
         specifier: ^10.0.1
         version: 10.0.1
-      '@opencord/shared':
-        specifier: workspace:*
-        version: link:../shared
       bcryptjs:
         specifier: ^2.4.3
         version: 2.4.3
@@ -102,12 +102,12 @@ importers:
 
   packages/web:
     dependencies:
+      '@backspace/shared':
+        specifier: workspace:*
+        version: link:../shared
       '@livekit/components-react':
         specifier: ^2.7.4
         version: 2.9.19(livekit-client@2.17.1(@types/dom-mediacapture-record@1.0.22))(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(tslib@2.8.1)
-      '@opencord/shared':
-        specifier: workspace:*
-        version: link:../shared
       '@sapphi-red/web-noise-suppressor':
         specifier: ^0.3.5
         version: 0.3.5