github: add support-request automation workflow

Add workflow that automatically closes issues labeled as
support-request with a message directing users to Discord
for configuration and support questions.

The workflow:
- Triggers when support-request label is added
- Posts a comment explaining this tracker is for bugs/features
- Links to documentation and Discord
- Closes the issue as "not planned"

.github/label-response/support-request.md

@@ -0,0 +1,15 @@
+Thank you for reaching out.
+
+This issue tracker is used for **bug reports and feature requests** only. Your question appears to be a support or configuration question rather than a bug report.
+
+For help with setup, configuration, or general questions, please visit our [Discord community](https://discord.gg/c84AZQhmpx) where the community and maintainers can assist you in real-time.
+
+**Before posting in Discord, please check:**
+
+- [Documentation](https://headscale.net/)
+- [FAQ](https://headscale.net/stable/faq/)
+- [Debugging and Troubleshooting Guide](https://headscale.net/stable/ref/debug/)
+
+If after troubleshooting you determine this is actually a bug, please open a new issue with the required debug information from the troubleshooting guide.
+
+This issue has been automatically closed.