feat(Map): add custom marker rendering with renderMarker API

Implements flexible custom marker rendering following Material-UI DataGrid
and Ant Design Table patterns. Enables developers to provide custom React
components for map markers while the library handles all Leaflet integration.

Core Changes:
- Add renderMarker prop to Map, MapView, and CompactMap components
- Add RenderMarkerParams interface with location, state, color, and variant
- Implement three-tier priority: per-location → global → built-in markers
- Support null returns from renderMarker to fall back to built-in markers
- Export RenderMarkerParams in public API via index.ts

Performance Optimizations:
- Remove react-dom/server dependency (~50KB bundle reduction)
- Implement lightweight SVG serializer for client-side conversion
- Automatically extract icon size/anchor from SVG width/height attributes
- Fix marker alignment issues for non-standard sizes (e.g., 20×20 dots)

API Design:
- Global renderMarker: applies to all locations unless overridden
- Per-location renderMarker: location-specific customization via LocationData
- Null fallback pattern: return null to use built-in markers for specific states
- Hybrid mode support: different markers for selected/unselected via variant param

Examples Added (CustomMarkers.stories.tsx):
1. Global Custom Marker - uniform styling across all locations
2. Hybrid Mode Support - pin when selected, dot otherwise
3. Per-Location Custom Markers - unique markers per location
4. Performance Optimized - useCallback memoization pattern
5. Fallback Pattern - custom selected, default unselected

Technical Details:
- Automatic size/anchor calculation: iconAnchor=[w/2, h], popupAnchor=[0, -h]
- React prop transformations: className→class, strokeWidth→stroke-width, etc.
- Recursive SVG child serialization for complex marker structures
- SSR-safe (MapView already guards against server-side rendering)

Fixes:
- CompactMap now forwards renderMarker prop to MapView
- Fixed marker positioning for non-28×40 sized custom markers
- Removed server-side React bundle bloat from client code

Author: JakeLin

packages/ui/src/components/Map/CompactMap.tsx

@@ -63,6 +63,7 @@ export const CompactMap: React.FC<CompactMapProps> = ({
   defaultCenter,
   defaultZoom,
   markerVariant,
+  renderMarker,
   isInspectorOpen,
   loading = false,
   error = false,
@@ -93,6 +94,7 @@ export const CompactMap: React.FC<CompactMapProps> = ({
           defaultCenter={defaultCenter}
           defaultZoom={defaultZoom}
           markerVariant={markerVariant}
+          renderMarker={renderMarker}
           isInspectorOpen={isInspectorOpen}
           loading={loading}
           error={error}