feat: add macOS build, Docker image, and CI workflows

macOS (.dmg):
- Add mac build config to apps/desktop/package.json (x64 + arm64 DMGs)
- .github/workflows/build-mac.yml — builds on macos-latest, uploads to release

Docker (headless scheduler + web remote):
- docker/server.js — Node.js entry point using homebridge-plugin lib;
  REST API + WebSocket, serves mobile web UI on PORT (default 3456)
- docker/package.json — production deps (adm-zip, axios, sql.js, ws, xml2js, xmlbuilder2)
- Dockerfile — node:20-alpine image; VOLUME /data for persistent config
- .github/workflows/build-docker.yml — builds linux/amd64+arm64,
  pushes to ghcr.io/k0rb3nd4ll4s/dibby-wemo-manager

Usage:
  docker run -d --network host -v /opt/wemo:/data \
    ghcr.io/k0rb3nd4ll4s/dibby-wemo-manager:latest

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/build-mac.yml

@@ -0,0 +1,52 @@
+name: Build & Upload macOS Package
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Release tag to upload assets to (e.g. v2.0.0)'
+        required: true
+        default: 'v2.0.0'
+
+jobs:
+  build-mac:
+    runs-on: macos-latest
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Install workspace dependencies
+        run: npm install --legacy-peer-deps
+
+      - name: Vite build
+        run: npx electron-vite build
+        working-directory: apps/desktop
+
+      - name: Bundle standalone scheduler
+        run: node scripts/bundle-standalone.js
+        working-directory: apps/desktop
+
+      - name: Build macOS packages
+        run: npx electron-builder --mac --publish never
+        working-directory: apps/desktop
+        env:
+          CSC_IDENTITY_AUTO_DISCOVERY: "false"
+
+      - name: List build output
+        run: ls -lh apps/desktop/dist/
+
+      - name: Upload macOS packages to release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ github.event.inputs.tag }}
+          files: apps/desktop/dist/*.dmg
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}