fix: Resolve temp directory permission issues for policy creation

- Changed default temp directory to local backend/temp instead of system temp
- Added write permission test during temp directory initialization
- Implemented fallback to OS temp directory if local temp fails
- Added unique random suffix to policy filenames to avoid conflicts
- Set proper file permissions (0o644) when writing policy files
- Improved error handling for temp directory creation failures
- Fixed fs.constants reference for file access checks

This resolves the EACCES permission denied error when creating policies
in Docker/production environments.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

.claude-flow/metrics/task-metrics.json

@@ -0,0 +1,10 @@
+[
+  {
+    "id": "cmd-hooks-1755632885292",
+    "type": "hooks",
+    "success": true,
+    "duration": 4.192417000000006,
+    "timestamp": 1755632885296,
+    "metadata": {}
+  }
+]