CI: use docker compose build --no-cache to prevent stale images

Replace build-push-action with docker compose build --no-cache to
ensure the image always contains the latest code. Remove buildx action
since we don't need it anymore.

.gitea/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: Build, Lint, and Test
+name: Build and Test
 
 on:
   push:
@@ -12,29 +12,22 @@ on:
 
 jobs:
   build-and-test:
-    name: Build, Lint, and Test
+    name: Build and Test
     runs-on: ubuntu-latest
     if: "! contains(toJSON(github.event.commits.*.message), '[skip ci]')"
     env:
       COMPOSE_FILE: ./docker-compose.ci.yml
       MIX_ENV: test
+      DOCKER_BUILDKIT: 1
 
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
-
-      - name: Build docker image
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          file: ./docker/dev.Dockerfile
-          load: true
-
-      - name: Run Docker image
-        run: docker compose up --detach
+      - name: Build and run Docker image
+        run: |
+          docker compose build --no-cache
+          docker compose up --detach
 
       - name: Install deps
         run: |