Read and render object records with thumbnails, search index, and source image footnotes

[colinangusmackay]

Summary

• Adds thumbnail generation (32px) alongside full-size media images when rendering GEDCOM object records
• Introduces a new search-index.json output containing all individuals with names, birth/death/marriage events, and residences — suitable for client-side search
• Source footnotes in Markdown now display inline thumbnail images for publishable JPG objects (suppressed for living persons)
• Cleans up commented-out debug code and minor code quality fixes

Changes

• RenderObjectHandler — refactored image rendering into a reusable private method; now renders both full-size and thumbnail variants
• RenderPersonIndexAsJsonHandler — new handler registered for RenderPersonIndex, writes search-index.json
• FileNamer — new methods: GetDestinationThumbnailFile, GetMediaThumbnailFile, GetSearchIndexJsonFile
• MarkdownFootnoteOrganiser — new WriteImages method appends thumbnails to source footnotes
• RenderSourceIndexAsMarkdownHandler — removed stale debug code
• Program.cs — registers RenderPersonIndexAsJsonHandler