feat(parse): extract shared upload utilities

[ze-mu-zhou]

Description

Extract encoding detection and file upload logic from CodeRepositoryParser._upload_directory() into a new shared module openviking/parse/parsers/upload_utils.py for reuse by the upcoming DirectoryParser (Issue #80, Discussion #83 T2).

Related Issue

Relates to #80
Discussion #83 (T2: shared upload utilities)

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• New openviking/parse/parsers/upload_utils.py with shared functions: is_text_file, detect_and_convert_encoding, should_skip_file, should_skip_directory, upload_text_files, upload_directory, with OS-independent path traversal protection via _sanitize_rel_path
• Refactored CodeRepositoryParser._upload_directory() from 108-line inline implementation to 3-line delegation to shared upload_directory
• Removed unused imports from code.py (ADDITIONAL_TEXT_EXTENSIONS, TEXT_ENCODINGS, UTF8_VARIANTS)

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

52 test cases covering all functions and edge cases (path traversal, encoding conversion, file filtering, upload failures, etc.)

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Additional Notes

This PR is the T2 sub-task from Discussion #83 (DirectoryParser RFC), providing shared infrastructure for the upcoming T3/T5 implementations.

[CLAassistant]

All committers have signed the CLA.