[main]: fix Dockerfile

.gitea/workflows/docker.yaml

@@ -3,6 +3,10 @@ name: Build and Push Docker Image
 on:
   push:
     branches: [ "main" ]
+  workflow_dispatch:
+
+env:
+  IMAGE_NAME: gitea.umbra.mom/ciaran/football-competitiveness
 
 jobs:
   build:
@@ -21,10 +25,18 @@ jobs:
             -u "$REGISTRY_USER" \
             --password-stdin
 
-      - name: Build image
+      - name: Set up buildx
         run: |
-          docker build -t gitea.umbra.mom/ciaran/football-competitiveness:latest .
+          docker buildx create --name ci-builder --driver docker-container --use || docker buildx use ci-builder
+          docker buildx inspect --bootstrap
 
-      - name: Push image
+      - name: Build and push image (with cache)
         run: |
-          docker push gitea.umbra.mom/ciaran/football-competitiveness:latest
+          docker buildx build \
+            --pull \
+            --platform linux/amd64 \
+            -t "${IMAGE_NAME}:latest" \
+            --cache-from "type=registry,ref=${IMAGE_NAME}:buildcache" \
+            --cache-to "type=registry,ref=${IMAGE_NAME}:buildcache,mode=max" \
+            --push \
+            .