Fixed Hindi README formatting and documentation

[TP-AdnanKhan]

Summary

Improved the Hindi translation of README.hi.md to make the documentation clearer, more consistent, and easier to understand for Hindi-speaking users.

The translation uses modern standard Hindi (मानक हिंदी) suitable for software documentation. Common technical terms such as Markdown, DOCX, API, AI, Python, Windows, and GitHub are kept in English where they are more familiar to developers.

Validation

• ruff check .
• mypy src/cleantext_studio
• pytest -q
• Relevant documentation, translation, or screenshot checks

Safety and compatibility

• No API key, private document, local path, build output, or binary is included.
• Existing cleanup behavior is unchanged, or a focused regression test explains the intentional change.
• UI changes include a privacy-safe screenshot when useful.