Fix ESLint fast-refresh warnings

Refactor to resolve react-refresh/only-export-components warnings:
- Move buttonVariants export to separate file (Button.variants.ts)
- Extract WebSocketContext to dedicated context file
- Move useWebSocketContext hook to separate file
- Update imports across affected files

All component files now export only components, improving fast refresh reliability

src/hooks/useWebSocket.ts

@@ -1,5 +1,6 @@
 import { useEffect, useRef } from 'react';
-import { useWebSocketContext, WSMessage } from '../providers/WebSocketProvider';
+import { useWebSocketContext } from '../providers/useWebSocketContext';
+import { WSMessage } from '../providers/WebSocketProvider';
 
 // Re-export WSMessage type for convenience
 export type { WSMessage };