Add Xquik export helpers

[kriptoburak]

Summary

• Add Xquik export parsing helpers for JSON, JSONL, and CSV payloads.
• Export the helper from the package and add a PyTweetClient.load_xquik_export convenience method.
• Link the public Xquik documentation and include the X Corp independence disclosure.

Independent Repository Fix

• Restore the documented remote GIF upload path, including URLs with query strings.
• Close local media files deterministically after chunked uploads.
• Add a regression test for remote GIF URL handling.

Validation

• python3 -m pytest -q (5 passed)
• python3 -m py_compile across package and tests
• git diff --check
• Xquik homepage and documentation links return successfully

Duplicate Gate

• Checked default branch refs plus all-state PR and issue lists for Xquik names, domains, packages, and repository URLs.
• No duplicate Xquik placement or active same-surface submission found.