fix: resolve SSH permission issue in archive-to-main step

Problem: alpine/git:latest image lacks SSH client, causing git fetch to fail
Solution: Switch to node:20-alpine image and install git + openssh-client

This should complete the full CI/CD pipeline successfully.

.woodpecker.yml

@@ -161,7 +161,7 @@ steps:
         - release/**
 
   archive-to-main:
-    image: alpine/git:latest
+    image: node:20-alpine
     environment:
       SSH_PRIVATE_KEY:
         from_secret: ssh_private_key
@@ -169,6 +169,7 @@ steps:
       - build-and-deploy
     commands:
       - echo "Archiving to main branch"
+      - apk add --no-cache git openssh-client
       - mkdir -p ~/.ssh
       - echo "$SSH_PRIVATE_KEY" > ~/.ssh/id_rsa
       - chmod 600 ~/.ssh/id_rsa