feat: Try to build image in ci instead of relying on just.

.gitea/workflows/ci.yaml

@@ -14,11 +14,18 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
     - uses: actions/checkout@v4
-    - name: Setup just
-      uses: extractions/setup-just@v3
     - name: Setup QEMU
       uses: docker/setup-qemu-action@v3
     - name: Setup buildx
       uses: docker/setup-buildx-action@v3 
-    - name: Run tests
+    - name: Build test image
-      run: just docker_tag=test test-docker
+      uses: docker/build-push-action@v6
+      with:
+        context: .
+        file: docker/Dockerfile.test
+        push: false
+        load: true
+        tags: michael/ductcalc:test
+    - name: Run Tests
+      run: |
+        docker run --rm michael/ductcalc:test swift test