Add bilingual presentation pages

[justinyoo]

Summary

Add dedicated Korean and English Marp presentations, preserve the current slide when switching languages, and publish them under /ko/ and /en/. The root page now redirects to the English presentation while preserving query parameters and slide hashes.

Change type

• Presentation content
• Presentation design
• PowerShell
• Bash
• Bicep
• Documentation or repository maintenance

Validation

• Marp HTML generation succeeds.
• Updated slides were visually reviewed.
• PowerShell files parse without errors.
• Bash files pass bash -n.
• Bicep files build successfully.
• No generated files, credentials, or sensitive data are included.

Additional checks:

• Verified all 31 slides render in both languages.
• Verified each slide contains a language switch.
• Verified same-number slide navigation between /ko/ and /en/.
• Verified referenced images exist in both deployed asset directories.

Screenshots

Not included. The existing visual design is preserved; this change adds the language switch and bilingual routing.

Related issues

None.