fix: set read permissions on dist/ for nginx container

The nginx:alpine image runs as UID 101 which can't read
root-owned files from the CI build. chmod o+rX allows the
nginx user to serve the static files.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/deploy.yaml

@@ -31,6 +31,7 @@ jobs:
 
       - name: Deploy to nginx
         run: |
+          chmod -R o+rX dist
           docker rm -f slides-nginx 2>/dev/null || true
           docker run -d \
             --name slides-nginx \