Core: Enable hash-based change detection for notebook translator

[skytin1004]

Enable hash-based change detection for notebook translator

Purpose

Implements intelligent change detection for Jupyter notebook translation to optimize translation efficiency and ensure translations are always up-to-date. Previously, notebook translations couldn't detect when source files changed, leading to unnecessary re-translations or outdated translations.

Description

This PR adds comprehensive change detection capabilities to the notebook translator:

Key Features:

• Hash-based change detection: Compares original file hash with stored metadata to detect changes
• Smart translation skipping: Skips translation when notebooks are already up-to-date
• Automatic retranslation: Triggers retranslation when source files are modified
• Metadata integration: Adds coopTranslator metadata to translated notebooks for tracking
• File type awareness: Ensures retranslation logic uses correct translator (notebook vs markdown)

Technical Changes:

• Moved notebook metadata functions from notebook_utils.py to metadata_utils.py for better organization
• Added add_notebook_metadata(), read_notebook_metadata(), and is_notebook_up_to_date() functions
• Enhanced JupyterNotebookTranslator to automatically add metadata after translation
• Fixed retranslate_outdated_files() to use appropriate translator based on file extension
• Added comprehensive test coverage for all new functionality

Related Issue

Closes #[issue_number] (if applicable)

Does this introduce a breaking change?

When developers merge from main and run the server, azd up, or azd deploy, will this produce an error?

• Yes
• No

This change is backward compatible. Existing translated notebooks without metadata will be treated as outdated and retranslated with the new metadata system.

Type of change

• Bugfix
• Feature
• Code style update (e.g., formatting, local variables)
• Refactoring (no functional or API changes)
• Documentation content changes
• Other... Please describe:

Checklist

Before submitting your pull request, please confirm the following:

• I have thoroughly tested my changes: I confirm that I have run the code and manually tested all affected areas.
• All existing tests pass: I have run all tests and confirmed that nothing is broken.
• I have added new tests (if applicable): I have written tests that cover the new functionality introduced by my code changes.
• I have followed the Co-op Translators coding conventions: My code adheres to the style guide and coding conventions outlined in the repository.
• I have documented my changes (if applicable): I have updated the documentation to reflect the changes where necessary.

Additional context

Files Modified:

• src/co_op_translator/utils/common/metadata_utils.py - Added notebook metadata functions
• src/co_op_translator/core/llm/jupyter_notebook_translator.py - Added metadata integration
• src/co_op_translator/core/project/translation_manager.py - Enhanced retranslation logic
• tests/ - Added comprehensive test coverage

Testing:

• ✅ All existing tests pass
• ✅ New tests cover metadata functions, notebook translation, and change detection
• ✅ Manual testing confirms notebooks are correctly translated and tracked

Performance Impact:

• Significantly reduces unnecessary API calls for unchanged notebooks
• Minimal overhead from hash calculation and metadata operations
• Smart caching prevents redundant translations

This enhancement brings notebook translation in line with the existing markdown translation optimization, providing a consistent and efficient translation experience across all supported file types.

[skytin1004]

I have reviewed the changes and everything looks good.