feat: update media parsers

[MaojiaSheng]

Description

1. ✅ Updated sanitize_segment to support CJK characters (Japanese, Korean, etc.) in openviking_cli/utils/uri.py, openviking/parse/parsers/markdown.py, openviking/parse/parsers/html.py
2. ✅ split media parsers into image.py, video.py, audio.py, so that we can apply different strategies in the future
3. ✅ Added VikingURI.normalize() to auto-complete viking:// scheme in all relevant places in openviking_cli/client/http.py
4. ✅ Updated media parsers to:
   • Keep original filename (spaces replaced by underscores)
   • Create folder name with extension (like {filename}_{ext})
   • Add original_filename to node.meta
   • Update overview.md to reference original filename

Related Issue

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

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

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

Screenshots (if applicable)

Additional Notes

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1 out of 2 committers have signed the CLA.

✅ MaojiaSheng
❌ openviking

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