refactor(core): optimize state management and component rendering performance

Improve application stability and performance by optimizing Zustand store usage, implementing memoization patterns, and introducing persistent authentication.

- **State Management**:
  - Refactor Zustand selectors to use `useShallow` and `getState()` to prevent unnecessary re-renders and infinite loops in hooks.
  - Implement `persist` middleware for `authStore` to maintain user sessions across restarts.
  - Introduce `buildStateCached` in `themeStore` to reduce redundant theme object computations.
- **Performance & Rendering**:
  - Implement `useMemo` for stable object/array references in `ImageGallery` and list components to prevent expensive re-renders.
  - Replace inline arrow functions with `useCallback` in complex screens like `ChatScreen` and `MessageListScreen`.
  - Optimize `FlashList` usage by providing stable `key` and `extraData` props.
- **Architecture**:
  - Decouple unread count fetching by introducing `useUnreadCountQuery` (React Query) for better caching and synchronization.
  - Add `useChannels` hook to centralize channel data fetching.
  - Refine `SessionGate` logic to allow immediate rendering of authenticated users while verifying in the background.

src/screens/auth/RegisterScreen.tsx

@@ -77,7 +77,7 @@ export const RegisterScreen: React.FC = () => {
     resetRegisterData,
     goToNextStep,
     goToPrevStep,
-  } = useRegisterStore();
+  } = useRegisterStore.getState();
 
   // 本地状态
   const [loading, setLoading] = React.useState(false);