CI: lowercase image repository name; compose example too

Docker registry names must be lowercase, so PUBLIC/gpu-turnstile was
rejected by buildx. The workflow now lowercases gitea.repository.

.gitea/workflows/ci.yml

@@ -37,6 +37,12 @@ jobs:
             exit 1
           fi
 
+      - name: Compute lowercase image name
+        id: meta
+        run: |
+          REPO=git.rambossek.at/$(echo "${{ gitea.repository }}" | tr '[:upper:]' '[:lower:]')
+          echo "image=$REPO" >> "$GITHUB_OUTPUT"
+
       - uses: docker/setup-buildx-action@v3
 
       - uses: docker/login-action@v3
@@ -52,5 +58,5 @@ jobs:
           build-args: |
             VERSION=${{ gitea.ref_name }}
           tags: |
-            git.rambossek.at/${{ gitea.repository }}:${{ gitea.ref_name }}
+            ${{ steps.meta.outputs.image }}:${{ gitea.ref_name }}
-            git.rambossek.at/${{ gitea.repository }}:latest
+            ${{ steps.meta.outputs.image }}:latest

SPEC.md

@@ -194,7 +194,9 @@ are new.
      available in the runner image
   2. on a version tag only (`vX.Y.Z`, enforced): build the image with buildx
      and push it to the Gitea registry
-     `git.rambossek.at/<owner>/gpu-turnstile` tagged `:<tag>` and `:latest`.
+     `git.rambossek.at/<owner>/gpu-turnstile` tagged `:<tag>` and `:latest`
+     (the repository path is lowercased in the workflow; Docker registry
+     names must be lowercase).
      Login uses the repo secret `REGISTRY_TOKEN` (an access token with
      `write:package` scope) because the automatic `GITEA_TOKEN` cannot push
      packages; the username is just `gitea.actor`.
@@ -205,7 +207,7 @@ are new.
 
 ```yaml
   gpu-turnstile:
-    image: git.rambossek.at/<owner>/gpu-turnstile:v0.1.0
+    image: git.rambossek.at/<owner>/gpu-turnstile:v0.1.0  # owner lowercased, e.g. "public"
     environment:
       OLLAMA_URL: http://<workstation-ip>:11435
       COMFY_URL:  http://<workstation-ip>:8189

compose.yaml.example

@@ -4,7 +4,7 @@
 # Ollama and ComfyUI instances run one port higher on the workstation.
 services:
   gpu-turnstile:
-    image: git.rambossek.at/PUBLIC/gpu-turnstile:v0.1.1
+    image: git.rambossek.at/public/gpu-turnstile:v0.1.1
     restart: unless-stopped
     environment:
       OLLAMA_URL: http://<workstation-ip>:11435