feat(message): implement incremental sync and atomic unread updates

Refactor the messaging system to improve synchronization efficiency and state consistency.

- Implement incremental message synchronization using sequence numbers (seq) to reduce payload size.
- Add `markAllAsRead` batch API support to optimize read receipt processing.
- Introduce atomic state updates in `useMessageStore` to prevent inconsistent UI rendering during unread count changes.
- Implement notification deduplication in `WSMessageHandler` to prevent duplicate unread increments during reconnection.
- Optimize `MessageSyncService` to prioritize incremental sync over full snapshots when local data exists.
- Refactor `ReadReceiptManager` to use optimistic updates with proper rollback mechanisms.
- Fix minor UI issues in `SettingsScreen` and `PrivacySettingsScreen` related to theme picker z-index and style application.

src/screens/profile/PrivacySettingsScreen.tsx

@@ -333,7 +333,7 @@ export const PrivacySettingsScreen: React.FC = () => {
                               variant="body"
                               style={[
                                 styles.dropdownOptionText,
-                                isActive && styles.dropdownOptionTextActive,
+                                ...(isActive ? [styles.dropdownOptionTextActive] : []),
                               ]}
                             >
                               {option.label}

src/screens/profile/SettingsScreen.tsx

@@ -408,7 +408,7 @@ export const SettingsScreen: React.FC = () => {
     <View
       key={group.title}
       style={[
-        { overflow: 'visible', zIndex: group.items.some((i) => i.isThemePicker && openPicker === 'theme') ? 10 : groupIndex },
+        { overflow: 'visible', zIndex: group.items.some((i) => 'isThemePicker' in i && i.isThemePicker && openPicker === 'theme') ? 10 : groupIndex },
       ]}
     >
       <View style={styles.groupHeader}>