Gitea Actions Runner 동작 확인용 ping 워크플로 추가

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/ping.yml

@@ -0,0 +1,18 @@
+name: Ping (runner check)
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - '.gitea/workflows/ping.yml'
+  workflow_dispatch:
+
+jobs:
+  ping:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Say hello
+        run: |
+          echo "Runner is alive."
+          echo "OS: $(uname -a)"
+          echo "Node: $(node --version 2>/dev/null || echo 'not installed')"