Optimize Storage

Compact search index and flush database changes.

Prunes old LanceDB versions and runs a KuzuDB checkpoint.

curl -X POST "http://127.0.0.1:14242/storage/optimize"

{
  "success": true,
  "before_bytes": 0,
  "after_bytes": 0,
  "freed_bytes": 0,
  "message": ""
}