ci: allow dist/ in Docker build context

.dockerignore excluded dist, so plugins/docker never saw the SSR
output from the build step (COPY dist failed).

Co-authored-by: Cursor <cursoragent@cursor.com>

.dockerignore

@@ -1,5 +1,5 @@
 node_modules
-dist
+# dist is produced by CI and must be in the image context
 .git
 .env
 .env.*