feat(server): add Dockerfile + CI docker build/push (#10)

* feat: add server Docker image build (Dockerfile + GH Actions)

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

.github/workflows/docker-server.yml

@@ -0,0 +1,57 @@
+name: Docker (server)
+
+on:
+    pull_request:
+    push:
+        branches:
+            - main
+        tags:
+            - 'v*'
+    workflow_dispatch:
+
+concurrency:
+    group: docker-server-${{ github.ref }}
+    cancel-in-progress: true
+
+permissions:
+    contents: read
+    packages: write
+
+jobs:
+    build:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v4
+
+            - uses: docker/setup-qemu-action@v3
+            - uses: docker/setup-buildx-action@v3
+
+            - name: Log in to GHCR
+              if: github.event_name != 'pull_request'
+              uses: docker/login-action@v3
+              with:
+                  registry: ghcr.io
+                  username: ${{ github.actor }}
+                  password: ${{ secrets.GITHUB_TOKEN }}
+
+            - name: Docker metadata
+              id: meta
+              uses: docker/metadata-action@v5
+              with:
+                  images: ghcr.io/${{ github.repository }}-server
+                  tags: |
+                      type=ref,event=branch
+                      type=ref,event=tag
+                      type=sha
+
+            - name: Build and (optionally) push
+              uses: docker/build-push-action@v6
+              with:
+                  context: .
+                  file: server/Dockerfile
+                  platforms: linux/amd64,linux/arm64
+                  push: ${{ github.event_name != 'pull_request' }}
+                  tags: ${{ steps.meta.outputs.tags }}
+                  labels: ${{ steps.meta.outputs.labels }}
+                  cache-from: type=gha
+                  cache-to: type=gha,mode=max