refactor: separate Nakama provider concerns into context, refs, and state modules

- Extracted context contract to `contexts.ts` (NakamaContextType)
- Added strongly typed internal provider refs in `refs.ts`
  - socketRef: React.RefObject<Socket | null>
  - gameMetadataRef: React.RefObject<GameMetadata | null>
- Added `NakamaProviderState` in `states.ts` for React-managed provider state
  - session, socket, matchId, matchmakerTicket
- Refactored NakamaProvider to use new modular structure
  - Replaced scattered useState/useRef with structured internal state + refs
  - Updated onMatchData to use MatchDataMessage model
  - Replaced deprecated MutableRefObject typing with RefObject
  - Cleaned update patterns using `updateState` helper
- Updated imports to use new models and context structure
- Improved separation of responsibilities:
  - models = pure domain types
  - context = exposed provider API
  - refs = internal mutable runtime refs
  - state = provider-managed reactive state
- Ensured all Nakama provider functions fully typed and consistent with TS

This refactor improves clarity, type safety, and maintainability for the
Nakama real-time multiplayer provider.

src/interfaces/contexts.ts

@@ -0,0 +1,38 @@
+import {
+  Client,
+  Session,
+  Socket,
+} from "@heroiclabs/nakama-js";
+
+import {
+  ApiMatch,
+  ApiLeaderboardRecordList,
+// @ts-ignore
+} from "@heroiclabs/nakama-js/dist/api.gen"
+
+import {
+  GameMetadata,
+  MatchDataMessage,
+} from './models'
+
+
+export interface NakamaContextType {
+  client: Client;
+  socket: Socket | null;
+  session: Session | null;
+  matchId: string | null;
+
+  loginOrRegister(username?: string): Promise<void>;
+  logout(): Promise<void>;
+
+  joinMatchmaker(gameMetadata: GameMetadata): Promise<string>;
+  exitMatchmaker(gameMetadata: GameMetadata): Promise<void>;
+  joinMatch(matchId: string): Promise<void>;
+
+  sendMatchData(matchId: string, op: number, data: object): void;
+
+  onMatchData(cb: (msg: MatchDataMessage) => void): void;
+
+  getLeaderboardTop(): Promise<ApiLeaderboardRecordList>;
+  listOpenMatches(): Promise<ApiMatch[]>;
+}