perf: add Zustand selectors to prevent cascading re-renders

Replace all bare useAuthStore(), useBlockingStore(), and
useSuccessNotification() calls with individual field selectors.
This prevents components from re-rendering when unrelated store
fields change.

- 21 useAuthStore usages across 20 files: individual selectors
  for 1-2 fields, useShallow for 3+ fields
- 5 useBlockingStore usages: individual selectors
- 2 useSuccessNotification usages: individual selectors

src/providers/WebSocketProvider.tsx

@@ -9,7 +9,8 @@ export type { WSMessage } from './WebSocketContext';
 const isDev = import.meta.env.DEV;
 
 export function WebSocketProvider({ children }: { children: React.ReactNode }) {
-  const { accessToken, isAuthenticated } = useAuthStore();
+  const accessToken = useAuthStore((state) => state.accessToken);
+  const isAuthenticated = useAuthStore((state) => state.isAuthenticated);
   const wsRef = useRef<WebSocket | null>(null);
   const reconnectTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   const pingIntervalRef = useRef<ReturnType<typeof setInterval> | null>(null);