CI: build+push ArikTube container to ghcr.io on the arik branch

Gate first: crystal spec + format-strict build on 1.20.3 (mirrors
upstream ci.yml). Then a linux/amd64 image build pushed as
ghcr.io/neskiredk/invidious:latest + :sha-<commit>. No expiry label.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/build-arik-container.yml

@@ -0,0 +1,85 @@
+name: Build ArikTube container
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - arik
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          submodules: true
+
+      - name: Install required APT packages
+        run: sudo apt install -y libsqlite3-dev
+
+      - name: Install Crystal
+        uses: crystal-lang/install-crystal@v1.9.2
+        with:
+          crystal: 1.20.3
+
+      - name: Cache Shards
+        uses: actions/cache@v6
+        with:
+          path: |
+            ./lib
+            ./bin
+          key: shards-${{ hashFiles('shard.lock') }}
+
+      - name: Install Shards
+        run: |
+          if ! shards check; then
+            shards install --skip-postinstall --skip-executables
+          fi
+
+      - name: Run tests
+        run: crystal spec
+
+      - name: Build
+        run: crystal build --warnings all --error-on-warnings --error-trace src/invidious.cr
+
+  build:
+    needs: test
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v4
+
+      - name: Login to registry
+        uses: docker/login-action@v4
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v6
+        with:
+          images: ghcr.io/neskiredk/invidious
+          flavor: |
+            latest=false
+          tags: |
+            type=raw,value=latest
+            type=sha
+
+      - name: Build and push
+        uses: docker/build-push-action@v7
+        with:
+          context: .
+          file: docker/Dockerfile
+          platforms: linux/amd64
+          labels: ${{ steps.meta.outputs.labels }}
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          build-args: |
+            "release=1"