refactor(core): introduce MapEngineAdapter

[heritechie]

Goal:
Decouple core editor logic from any specific map engine implementation.

Tasks:

• Define MapEngineAdapter interface
• Move all map-engine-specific calls behind the adapter
• Ensure core editor does not import or reference Leaflet (or any engine)

Acceptance:

• Core builds without Leaflet dependency installed
• Adapter is the only integration point between core and map engine
• Editor initialization requires an adapter instance