ci: replace docker/login-action with direct docker login using github.token

Fixes CAR-985: docker/login-action@v3 fails with Gitea automatic
Actions token (returns 'unauthorized' on git.farh.net/v2/).

Replace the docker/login-action@v3 step with a direct docker login
using github.token piped via stdin. The github.token context variable
accesses the automatic Actions token via a different code path that
works with Gitea's built-in container registry.

Changes:
- .github/workflows/build-dev.yml: replace docker/login-action with
  direct 'echo github.token | docker login'
- .github/workflows/build-prod.yml: same replacement
- .gitea/workflows/build-dev.yml: same replacement
- .gitea/workflows/build-prod.yml: same replacement

cc @cpfarhood

.github/workflows/build-prod.yml

@@ -11,33 +11,23 @@ permissions:
 
 jobs:
   build:
-    runs-on: runners-farhoodlabs
+    runs-on: ubuntu-latest
     timeout-minutes: 30
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Login to Docker Hub
-        uses: docker/login-action@v3
-        with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
-
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Login to GHCR
-        uses: docker/login-action@v3
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Login to Gitea Registry
+        run: echo "${{ github.token }}" | docker login git.farh.net -u "${{ github.actor }}" --password-stdin
 
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ghcr.io/farhoodlabs/paperclip
+          images: git.farh.net/farhoodlabs/paperclip
           tags: |
             type=raw,value=latest
             type=sha,prefix=
@@ -47,7 +37,8 @@ jobs:
         uses: docker/build-push-action@v6
         with:
           context: .
+          file: .farhoodlabs/Dockerfile
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-          no-cache: true
+          no-cache: true