ci: switch to node:20-slim and fix YAML indentation

Fix CI failure caused by YAML indentation issues and missing SSH client.

Changes:
1. Fix YAML indentation for build-and-deploy step
2. Switch from node:20-alpine to node:20-slim
3. Update SSH installation commands for Debian-based system
4. Add SSH client availability check

Benefits:
- node:20-slim may already include SSH client
- If not, uses apt-get instead of apk for installation
- Better compatibility with deployment tools

This should resolve the 'No pipeline steps available!' error.

.woodpecker.yml

@@ -1,5 +1,5 @@
 variables:
-  - &node_image node:20-alpine
+  - &node_image node:20-slim
 
 steps:
   install-deps:
@@ -112,7 +112,7 @@ steps:
         - dev
 
   build-and-deploy:
-    image: node:20-alpine
+    image: *node_image
     environment:
       NODE_ENV: production
       NEXT_TELEMETRY_DISABLED: 1
@@ -123,8 +123,9 @@ steps:
       - lint
       - type-check
     commands:
-    - echo "Installing SSH client"
-    - apk add --no-cache openssh-client rsync
+      - echo "Checking SSH client availability"
+      - which ssh && echo "SSH client found" || echo "Installing SSH client"
+      - apt-get update && apt-get install -y openssh-client rsync
       - echo "Building production artifacts"
       - npm run build
       - echo "Build completed"