Update .gitea/workflows/build.yaml

Corrected terminology and docker login method

.gitea/workflows/build.yaml

@@ -7,23 +7,25 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-
       - uses: docker/setup-buildx-action@v3
-
+      - name: Set lowercase repo path
+        run: echo "REPO_LC=$(echo '${{ gitea.repository }}' | tr '[:upper:]' '[:lower:]')" >> $GITHUB_ENV
       - name: Login to Gitea Container Registry
-        run: echo "${{ secrets.GITEA_TOKEN }}" | docker login gitea.kansaigaijin.com -u ${{ gitea.repository_owner }} --password-stdin
-
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.kansaigaijin.com
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.docker_builder }}
       - name: Build and push backend
         uses: docker/build-push-action@v5
         with:
           context: ./backend
           target: runtime
           push: true
-          tags: gitea.kansaigaijin.com/${{ gitea.repository }}/backend:latest
-
+          tags: gitea.kansaigaijin.com/${{ env.REPO_LC }}/backend:latest
       - name: Build and push frontend
         uses: docker/build-push-action@v5
         with:
           context: ./frontend
           push: true
-          tags: gitea.kansaigaijin.com/${{ gitea.repository }}/frontend:latest
+          tags: gitea.kansaigaijin.com/${{ env.REPO_LC }}/frontend:latest