Redraw GeoJSON features after style changes

[arpitagarwal1301]

Fixes #1050.

Observe legacy GeoJSON features so style and geometry changes invalidate the cached renderer model and redraw map objects with the updated values. Repeated insertion remains idempotent, removed features detach their observer, and null-geometry features remain safe across the layer lifecycle.

Multi-geometries now keep their rendered children under the parent feature, preserving complete removal and click lookup. Multi-polygons also carry their polygon style into the renderer.

Tests:

• data module unit tests, including focused redraw and renderer ownership regressions
• data module lint
• data debug assembly
• diff whitespace check