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-docker.yml

@@ -0,0 +1,43 @@
+name: Build & Push Docker Image
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Docker image tag (e.g. 2.0.0)'
+        required: true
+        default: '2.0.0'
+
+jobs:
+  build-docker:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile
+          push: true
+          platforms: linux/amd64,linux/arm64
+          tags: |
+            ghcr.io/k0rb3nd4ll4s/dibby-wemo-manager:${{ github.event.inputs.tag }}
+            ghcr.io/k0rb3nd4ll4s/dibby-wemo-manager:latest
+          cache-from: type=gha
+          cache-to: type=gha,mode=max