feat(docker): add Docker container for the agent (salvage #1841) (#3668)

Adds a complete Docker packaging for Hermes Agent:
- Dockerfile based on debian:13.4 with all deps
- Entrypoint that bootstraps .env, config.yaml, SOUL.md on first run
- CI workflow to build, test, and push to DockerHub
- Documentation for interactive, gateway, and upgrade workflows

Closes #850, #913.

Changes vs original PR:
- Removed pre-created legacy cache/platform dirs from entrypoint
  (image_cache, audio_cache, pairing, whatsapp/session) — these are
  now created on demand by the application using the consolidated
  layout from get_hermes_dir()
- Moved docs from docs/docker.md to website/docs/user-guide/docker.md
  and added to Docusaurus sidebar

Co-authored-by: benbarclay <benbarclay@users.noreply.github.com>

.github/workflows/docker-publish.yml

@@ -0,0 +1,61 @@
+name: Docker Build and Publish
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: docker-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile
+          load: true
+          tags: nousresearch/hermes-agent:test
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Test image starts
+        run: |
+          docker run --rm \
+            -v /tmp/hermes-test:/opt/data \
+            --entrypoint /opt/hermes/docker/entrypoint.sh \
+            nousresearch/hermes-agent:test --help
+
+      - name: Log in to Docker Hub
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Push image
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile
+          push: true
+          tags: |
+            nousresearch/hermes-agent:latest
+            nousresearch/hermes-agent:${{ github.sha }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max