fix: use origin/main workflow with env vars for registry credentials

Resolved merge conflicts by using current origin/main workflow which:
- Includes test job (npm ci + npm test)
- Has delete old latest image step
- Uses --build-arg for COMMIT_SHA
- Uses env vars for registry credentials (FORGEJO_REGISTRY_USER/TOKEN)

All features from main preserved, registry login fixed.

.gitea/workflows/build-push.yml

@@ -1,12 +1,14 @@
-name: Build & Push Portfolio Image
+name: CI
 
 on:
   push:
-    branches:
+    branches: [main]
-      - main
   pull_request:
-    branches:
+    branches: [main]
-      - main
+
+env:
+  REGISTRY: forgejo.riotpiao.com
+  IMAGE: forgejo.riotpiao.com/rock/portfolio
 
 jobs:
   test:
@@ -30,9 +32,6 @@ jobs:
     needs: test
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     runs-on: node
-    env:
-      REGISTRY: forgejo.riotpiao.com
-      IMAGE: forgejo.riotpiao.com/rock/portfolio
     steps:
       - name: Install Node.js and Docker
         run: |