feat: launch readiness — PWA, API hardening, memory leak fixes, sticker removal

- Add PWA infrastructure: vite-plugin-pwa, manifest, service worker,
  SW update prompt component, placeholder icons, Apple meta tags
- Harden API client: 401 auto-logout, AbortController timeouts
  (30s standard, 120s uploads), onUnauthorized callback
- Fix memory leaks: clear voice user status on leave, clean up all
  Maps (channelToSpaceMap, permissions, etc.) on removeSpace
- Upgrade error boundary to Aether Drift design with Try Again button,
  collapsible stack trace, and componentDidCatch logging
- Configure desktop icon paths in electron-builder.yml
- Remove sticker feature (server routes, schema, types, UI components)
- Fix Docker build: use **/node_modules in .dockerignore to prevent
  COPY from clobbering pnpm-installed workspace dependencies
- Add vite-env.d.ts declarations for noise suppressor wasm imports
- Exclude test files from tsc build via tsconfig

Dockerfile

@@ -27,7 +27,7 @@ COPY packages/server/ packages/server/
 COPY packages/web/ packages/web/
 
 # Build the web frontend
-RUN cd packages/web && pnpm run build
+RUN pnpm --filter @backspace/web build
 
 # ============================================================
 # Stage 2: Production runtime