Replace global mutable map store with React-compatible pattern

[tmshv]

Problem

src/map.ts uses a module-level mutable Map to store MapLibre map instances:

const store = new Map<string, maplibregl.Map>()

This breaks React's unidirectional data flow, makes testing difficult (no way to mock/reset between tests), and creates an implicit dependency that's hard to trace.

What needs to change

Consider replacing with:

• A React Context that provides the map instance(s), or
• Storing the map ref in Redux (as a non-serializable value), or
• Using react-map-gl's built-in useMap() hook (from MapProvider) consistently throughout the codebase