fix(ci): fix black/ruff failures, add CoC and PR template

- Fix Python formatting (sync no longer strips blank lines from .py files)
- Remove test_community_build.py (tests private sync module)
- Fix ruff warnings in test files
- Add CODE_OF_CONDUCT.md
- Add .github/PULL_REQUEST_TEMPLATE.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/n8n/plugin.py

@@ -12,6 +12,7 @@ from plugins.base import BasePlugin
 from plugins.n8n import handlers
 from plugins.n8n.client import N8nClient
 
+
 class N8nPlugin(BasePlugin):
     """
     n8n Automation Plugin - Comprehensive workflow management.