Remove overlay filesystem functionality and add detection/removal capability

- Remove unused overlay filesystem configuration and references
- Remove overlayfs sections from all profile JSON files
- Remove OVERLAY_ENABLED/OVERLAY_PROTECT_CONFIGS from config
- Update documentation to focus on tmpfs optimization
- Add overlay detection and removal functionality for cleanup
- Add remove_overlays() function with safe unmounting
- Add overlay status reporting in final optimization summary
- Add test-overlay-detection.sh for testing detection logic
- Simplify codebase by removing complex unused features
- Focus on proven desktop optimizations (tmpfs, zram, kernel)

profiles/development.json

@@ -58,14 +58,6 @@
       "fs.file-max": 2097152,
       "fs.inotify.max_user_watches": 524288,
       "kernel.pid_max": 32768
-    },
-    "overlayfs": {
-      "enabled": true,
-      "protect_configs": true,
-      "overlay_paths": [
-        "/home/*/workspace",
-        "/opt/projects"
-      ]
     }
   },
   "development_specific": {