feat: implement persistent notification system

- Added notifications table with auto-migration on startup.

- Created backend endpoints for fetching and managing notifications.

- Implemented interactive notification tray in the header with unread badges.

- Added automated triggers for organization creation and user registration completion.

services/dataService.ts

@@ -17,6 +17,45 @@ const getHeaders = () => {
   };
 };
 
+export const getNotifications = async (): Promise<any[]> => {
+  try {
+    const response = await fetch(`${API_URL}/notifications`, {
+      headers: getHeaders()
+    });
+    if (!response.ok) throw new Error('Failed to fetch notifications');
+    return await response.json();
+  } catch (error) {
+    console.error("API Error (getNotifications):", error);
+    return [];
+  }
+};
+
+export const markNotificationAsRead = async (id: string): Promise<boolean> => {
+  try {
+    const response = await fetch(`${API_URL}/notifications/${id}`, {
+      method: 'PUT',
+      headers: getHeaders()
+    });
+    return response.ok;
+  } catch (error) {
+    console.error("API Error (markNotificationAsRead):", error);
+    return false;
+  }
+};
+
+export const markAllNotificationsAsRead = async (): Promise<boolean> => {
+  try {
+    const response = await fetch(`${API_URL}/notifications/read-all`, {
+      method: 'PUT',
+      headers: getHeaders()
+    });
+    return response.ok;
+  } catch (error) {
+    console.error("API Error (markAllNotificationsAsRead):", error);
+    return false;
+  }
+};
+
 export const searchGlobal = async (query: string): Promise<{ members: User[], teams: any[], attendances: any[], organizations?: any[] }> => {
   try {
     const response = await fetch(`${API_URL}/search?q=${encodeURIComponent(query)}`, {