feat: add deployment steps for Docker build, login, and publish to Forgejo

.woodpecker/deployment.yaml

@@ -0,0 +1,20 @@
+steps:
+  - name: build-docker
+    image: docker:latest
+    commands:
+      - docker build -f backend.Dockerfile -t backend .
+
+  - name: login-forgejo
+    image: docker:latest
+    commands:
+      - docker login -u $$FORGEJO_USERNAME -p $$FORGEJO_PASSWORD git.mixel.cloud
+    secrets:
+      - FORGEJO_USERNAME
+      - FORGEJO_PASSWORD
+
+  - name: publish-forgejo
+    image: docker:latest
+    commands:
+      - export IMAGE_NAME=git.mixel.cloud/Turbo/peer-group-grading:$${CI_COMMIT_SHA:0:8}
+      - docker tag backend $$IMAGE_NAME
+      - docker push $$IMAGE_NAME