Add NFT media handler deployment report

[JOY (JOY)]

Summary

• add a self-contained Vietnamese dark-theme report for the deployed NFT Media Handler
• document GCS compatibility, Avalanche L1 suitability, cost, credentials, bucket policy, and rollout evidence
• keep the report inside the frontend repository under docs/

Validation

• git diff --check
• no em dash or en dash
• rendered through a local HTTP server with Playwright
• dark color-scheme and console verified
• independent Codex review: no actionable findings

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.