feat(ui): unify design system to Twitter/X style across screens and improve message handling

Redesign multiple screens and components from card-based responsive design to Twitter/X flat design:
- UserProfileHeader: adopt Twitter/X style with larger icons, simplified buttons, and block functionality
- AppBackButton: update to chevron-left icon with larger size, remove background styling
- Update SettingsScreen, EditProfileScreen, and UserProfileScreen with flat layout approach
- ConversationListRow: convert from bordered cards to flat list rows with updated typography

Improve message system with WebSocket notification handling:
- Add real-time system unread count updates via WebSocket
- Track lastSystemMessageAt for accurate system message timestamps
- Add notification deduplication and read-status filtering
- Combine system and conversation unread counts in background sync
- Clear system notifications from notification center on mark as read

src/stores/message/store.ts

@@ -31,6 +31,9 @@ export interface MessageState {
   totalUnreadCount: number;
   systemUnreadCount: number;
 
+  // 最后一条系统通知时间
+  lastSystemMessageAt: string | null;
+
   // 连接状态
   isWSConnected: boolean;
 
@@ -75,6 +78,7 @@ export interface MessageActions {
   addMessage: (conversationId: string, message: MessageResponse) => void;
   updateMessage: (conversationId: string, messageId: string, updates: Partial<MessageResponse>) => void;
   setUnreadCount: (total: number, system: number) => void;
+  setLastSystemMessageAt: (time: string | null) => void;
   setSSEConnected: (connected: boolean) => void;
   setCurrentConversation: (conversationId: string | null) => void;
   setLoading: (loading: boolean) => void;
@@ -95,6 +99,7 @@ const initialState: MessageState = {
   messagesMap: new Map(),
   totalUnreadCount: 0,
   systemUnreadCount: 0,
+  lastSystemMessageAt: null,
   isWSConnected: false,
   currentConversationId: null,
   isLoadingConversations: false,
@@ -160,6 +165,7 @@ export const useMessageStore = create<MessageStore>((set, get) => ({
       messagesMap: state.messagesMap,
       totalUnreadCount: state.totalUnreadCount,
       systemUnreadCount: state.systemUnreadCount,
+      lastSystemMessageAt: state.lastSystemMessageAt,
       isWSConnected: state.isWSConnected,
       currentConversationId: state.currentConversationId,
       isLoadingConversations: state.isLoadingConversations,
@@ -314,6 +320,10 @@ export const useMessageStore = create<MessageStore>((set, get) => ({
     set({ totalUnreadCount: total, systemUnreadCount: system });
   },
 
+  setLastSystemMessageAt: (time: string | null) => {
+    set({ lastSystemMessageAt: time });
+  },
+
   setSSEConnected: (connected: boolean) => {
     set({ isWSConnected: connected });
   },