Replaces 10 unique Unsplash hotlinked URLs (12 HTML occurrences across 9 pages) with local copies in images/hero/.
Removes external dependency on images.unsplash.com -- improves perf for Madagascar audience (lower latency vs CDN Unsplash) and ensures site availability if Unsplash CDN policies change.
Total added: ~2.5MB across 10 JPG files.
Refs: MVA WordPress -> static migration plan, Phase B PR #1.
