fix: CI/CD workflow - fix Docker repository name case sensitivity issue

The Docker registry requires repository names to be lowercase.
Fixed by converting the Gitea repository owner to lowercase for image tags
while keeping the original case for authentication purposes.

.gitea/workflows/docker-build.yml

@@ -11,6 +11,8 @@ env:
   GO_VERSION: "1.25"
   REGISTRY: gitea.mrixs.me
   IMAGE_NAME: naviwatcher
+  # Convert repository owner to lowercase for Docker compatibility
+  REPO_OWNER_LOWER: ${{ toLower(gitea.repository_owner) }}
 
 jobs:
   test:
@@ -90,7 +92,7 @@ jobs:
           context: .
           push: true
           tags: |
-            ${{ env.REGISTRY }}/${{ gitea.repository_owner }}/${{ env.IMAGE_NAME }}:latest
+            ${{ env.REGISTRY }}/${{ env.REPO_OWNER_LOWER }}/${{ env.IMAGE_NAME }}:latest
-            ${{ env.REGISTRY }}/${{ gitea.repository_owner }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
+            ${{ env.REGISTRY }}/${{ env.REPO_OWNER_LOWER }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
-          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ gitea.repository_owner }}/${{ env.IMAGE_NAME }}:buildcache
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.REPO_OWNER_LOWER }}/${{ env.IMAGE_NAME }}:buildcache
-          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ gitea.repository_owner }}/${{ env.IMAGE_NAME }}:buildcache,mode=max
+          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.REPO_OWNER_LOWER }}/${{ env.IMAGE_NAME }}:buildcache,mode=max