Update releases and readme

[rahlk]

Motivation and Context

This PR prepares the repository for the upcoming v1.0.0 release.

Specifically:

• Introduces global and backend-specific SemVer version tracking via pyproject.toml.
• Aligns release automation with Python packaging standards.
• Cleans up the README to focus only on Python SDK usage, removing backend-internal details.

This work ensures that the repository has a clean, professional structure and supports consistent versioning and publishing going forward.

How Has This Been Tested?

• Confirmed that pyproject.toml metadata is correctly structured.
• Confirmed that all the unit tests run correctly and the code coverage threshold is met.
• Verified README renders correctly with updated installation and quickstart instructions.

Breaking Changes

No breaking changes to existing functionality. However, users and contributors will see a restructured README and new project metadata organization.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the Codellm-Devkit Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

• The [tool.backend-versions] section inside pyproject.toml tracks backend-specific internal versions (Java and codeanalyzer for now).
• The README now clearly separates end-user SDK documentation from contributor/backend notes.
• Future backend upgrades will simply require incrementing their specific versions inside pyproject.toml without affecting the global SDK SemVer unless there is a user-visible change.