fix(islands): load islands that do not belong to any regency

[fityannugroho]

Summary

Ensure islands that are not assigned to any regency are loaded and displayed on the map. Also improve island marker rendering, clustering behavior, and popup content to make islands more discoverable and metadata more accurate.

What changed

• Fix loading logic so islands without a matching regency are included in the dataset and map layer.
• Improve island marker styling and clustering so markers remain visible and clustered sensibly across zoom levels.
• Fix popup / IslandsInfo content to show correct island metadata and clearer labels.
• Minor code cleanup and linting on island-related components.

Files / components touched (high level)

• modules/MapDashboard/IslandMarkers.tsx
• modules/MapDashboard/IslandsInfo.tsx
• modules/MapDashboard/MapView.tsx
• components/MapMarkerClusterGroup.tsx