Harden request handling and PyPI README

[Skhendle]

Motivation

• Make HTTP request handling more robust by handling non-JSON success responses and empty bodies gracefully.
• Standardize Authorization header casing to match common servers (Bearer) and avoid subtle auth bugs.
• Prefer explicit query parameter usage and ensure request models are serialized before sending JSON to avoid malformed requests.
• Improve README to be PyPI-friendly and provide stable links to demo and guidance docs.

Description

• Update BaseClient (src/userverse_python_client/http_client_base.py) to set Authorization: Bearer <token>, return None for empty bodies, and fall back to resp.text when resp.json() fails.
• Serialize request models by calling model_dump(exclude_none=True) in UverseUserClient (src/userverse_python_client/clients/user.py) for create_user and update_user, and use params for verify_user and password-reset endpoints.
• Replace manual query-string construction in UverseCompanyClient (src/userverse_python_client/clients/company.py) with explicit params handling and call _request("GET", "/company", params=...).
• Update docs: make README.md PyPI-friendly with python -m pip install ... and stable repo links, and refresh docs/other-language-clients.md to reflect Bearer casing, non-JSON success fallback, and preferring explicit query parameter handling.

Testing

• No automated tests were run for these changes.

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