fix: Resolve Docker temp directory permission issues

- Updated Dockerfile to create local temp directory with proper permissions
- Added volume mount for backend/temp in docker-compose.yml
- Improved temp directory fallback logic with multiple alternatives
- Added unique timestamps to test files to avoid conflicts
- Better logging to identify which temp directory is being used
- Try process.cwd()/temp before falling back to OS temp directory

This should resolve the persistent EACCES permission errors in Docker
containers by ensuring the backend uses a writable temp directory.

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

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

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

@@ -1,10 +1,10 @@
 [
   {
-    "id": "cmd-hooks-1755632885292",
+    "id": "cmd-hooks-1755633733484",
     "type": "hooks",
     "success": true,
-    "duration": 4.192417000000006,
-    "timestamp": 1755632885296,
+    "duration": 4.695624999999993,
+    "timestamp": 1755633733488,
     "metadata": {}
   }
 ]