Updated GitHub issue templates.

Thanks to xet7 !

.github/ISSUE_TEMPLATE/security-report.md

@@ -0,0 +1,14 @@
+name: 🛡️ Security Issue
+description: Report a security vulnerability
+labels: ["security", "critical"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        ## ⚠️ IMPORTANT: Please do not report security vulnerabilities via public issues.
+        
+        To protect the Wekan community, we ask that you report security bugs privately. This allows us to fix the issue before it can be exploited by malicious actors.
+        
+        ### How to report:
+        Please read our **[Security Policy (SECURITY.md)](https://github.com/wekan/wekan/blob/main/SECURITY.md)** for the official reporting process and contact information.
+