feat: render full map content (image, intro, markers) in PagedJS

- Fix template check 'carte' → 'map' so map subpages are served by API
- Add parseMarker() and enrich parseCarte() with static image, intro, markers
- Include map children in parseGeoformat() alongside chapters
- Resolve map block references in chapters to full carte data
- Update narrative store flattening with new carte fields
- Replace MapBlock placeholder with full carte rendering (title, image, tags, intro, markers with icons and blocks)
- Add default marker-pin.svg for markers without custom icon

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/assets/svg/marker-pin.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" width="24" height="24" fill="currentColor"><path d="M12 2C8.13 2 5 5.13 5 9c0 5.25 7 13 7 13s7-7.75 7-13c0-3.87-3.13-7-7-7zm0 9.5a2.5 2.5 0 1 1 0-5 2.5 2.5 0 0 1 0 5z"/></svg>