docs: add contributor and security guidelines

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,40 @@
+---
+name: Bug report
+about: Report a reproducible problem in Crucix
+title: "[Bug] "
+labels: bug
+assignees: ""
+---
+
+## Summary
+
+Describe the bug clearly.
+
+## Environment
+
+- OS:
+- Install method: local / Docker / other
+- Node version:
+- LLM provider:
+
+## Steps to Reproduce
+
+1.
+2.
+3.
+
+## Expected Behavior
+
+What should have happened?
+
+## Actual Behavior
+
+What happened instead?
+
+## Logs or Screenshots
+
+Paste relevant logs, screenshots, or terminal output.
+
+## Additional Context
+
+Anything else that helps narrow this down.