Fix Leaflet IIIF image viewer

[ewlarson]

Summary

• Route iiif_image resources through the Leaflet viewer instead of synthesizing a Mirador manifest.
• Replace the plugin-dependent IIIF path with a local IIIF Image API tile layer modeled after the abcdefgeo implementation.
• Fetch info.json, compute native zoom, build L.CRS.Simple image bounds from pixel dimensions, constrain panning with padded max bounds, and refit on layout changes.
• Avoid adding a basemap/geosearch path for IIIF image viewers, preventing stray basemap imagery tile requests.
• Explicitly import the Leaflet fullscreen plugin and keep fullscreen/opacity controls available for IIIF images.

Why

IIIF Image API resources need Leaflet's simple image coordinate space, not geospatial basemap coordinates. The earlier fix selected CRS.Simple, but it still relied on leaflet-iiif lifecycle behavior and did not compute the image bounds from info.json before fitting/constraining the map. That led to rough panning/zooming behavior and impossible tile requests.

Impact

Image-service-only IIIF resources can render as bounded image maps with predictable zoom and pan behavior, while IIIF Presentation manifests continue to use Mirador and normal geospatial Leaflet resources continue through the GeoBlacklight path.

Validation

• npm test -- run src/__tests__/geoblacklight/leaflet_viewer_controller.test.js src/__tests__/components/resource/ResourceViewer.test.tsx
• npm run build