Force IPv4 for SSH connections to the deploy host

aquaria.haemka.net has both A and AAAA records; the runner container has
no IPv6 route, so ssh picked the AAAA address and failed with 'Network
is unreachable'. Force -4 on both the keyscan and the actual rsync
connection.

.gitea/workflows/build-deploy.yml

@@ -32,7 +32,7 @@ jobs:
           printf '%s\n' "$DEPLOY_SSH_KEY" > ~/.ssh/deploy_key
           chmod 600 ~/.ssh/deploy_key
           ssh-keyscan -H git.haemka.in >> ~/.ssh/known_hosts
-          ssh-keyscan -H -p "${DEPLOY_PORT:-22}" "$DEPLOY_HOST" >> ~/.ssh/known_hosts
+          ssh-keyscan -4 -H -p "${DEPLOY_PORT:-22}" "$DEPLOY_HOST" >> ~/.ssh/known_hosts
 
       - name: Fetch theme submodule
         run: |
@@ -57,5 +57,5 @@ jobs:
           DEPLOY_PATH: ${{ vars.DEPLOY_PATH }}
         run: |
           rsync -avz --delete \
-            -e "ssh -i ~/.ssh/deploy_key -p ${DEPLOY_PORT:-22} -o StrictHostKeyChecking=yes" \
+            -e "ssh -4 -i ~/.ssh/deploy_key -p ${DEPLOY_PORT:-22} -o StrictHostKeyChecking=yes" \
             output/ "${DEPLOY_USER}@${DEPLOY_HOST}:${DEPLOY_PATH}"