feat: Graphql client memory optimization

[abelonogov-ld]

Summary

Do not produce byte array multiple times and close connection

---

Note

Avoids repeated byte-array allocations, uses fixed-length streaming with explicit Content-Length, and always disconnects the HTTP connection.

• Networking (GraphQLClient.kt):
  • Optimize request construction and streaming:
    • Precompute requestBytes (UTF-8) once; use for Content-Length, setFixedLengthStreamingMode, and output stream writes.
    • Remove redundant writes/flushes and avoid multiple toByteArray() calls.
  • Connection handling:
    • Use local connectionLocal with a finally block to disconnect() the HttpURLConnection.
  • Minor cleanup:
    • Remove unused Dispatchers import.
    • Consistent use of connectionLocal for response/error streams.

^{Written by Cursor Bugbot for commit 298a739. This will update automatically on new commits. Configure here.}