fix: use node:22-alpine for lint job

markdownlint-cli2 image runs as non-root, blocking apk install.
Use node-alpine base with npx instead.

.gitea/workflows/ci.yml

@@ -9,14 +9,14 @@ on:
 jobs:
   lint:
     runs-on: linux
-    container: docker.io/davidanson/markdownlint-cli2:v0.17.2
+    container: node:22-alpine
     steps:
       - run: apk add --no-cache git
       - run: |
           git clone --depth 1 \
             -c "http.extraHeader=Authorization: token ${{ github.token }}" \
             "${{ github.server_url }}/${{ github.repository }}.git" .
-      - run: markdownlint-cli2 "**/*.md"
+      - run: npx markdownlint-cli2 "**/*.md"
 
   link-check:
     runs-on: linux