ci: track .dockerignore (was caught by gitignore)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ttpears

.dockerignore

@@ -0,0 +1,12 @@
+node_modules
+dist
+dist-mcpb
+.git
+.gitignore
+*.md
+docs
+.env*
+.DS_Store
+*.log
+mcpb
+assets