feat: high-quality video/audio defaults for Sunbeam

- VP9 @ 1080p/8Mbps/30fps (was VP8 720p/1.7Mbps)
- 320kbps stereo Opus audio (was 48kbps mono)
- Screen share @ 1080p/60fps/8Mbps (was 30fps/5Mbps)
- VP9 SVC replaces simulcast (single stream with embedded layers)
- Auto VP8 fallback for incompatible clients

Dockerfile.sunbeam

@@ -0,0 +1,17 @@
+FROM --platform=$BUILDPLATFORM node:24-alpine AS build
+
+WORKDIR /app
+COPY package.json yarn.lock .yarnrc.yml ./
+COPY .yarn .yarn
+RUN corepack enable && yarn install --immutable
+
+COPY . .
+RUN yarn build:full
+
+# Compress assets for nginx gzip_static
+WORKDIR /app/dist/assets
+RUN gzip -k ../index.html *.js *.map *.css *.wasm *-app-*.json 2>/dev/null || true
+
+FROM nginxinc/nginx-unprivileged:alpine-slim
+COPY --from=build /app/dist /app
+COPY config/nginx.conf /etc/nginx/conf.d/default.conf