feat: implement categorized global search with RBAC

- Added /api/search endpoint with strict role-based data isolation.

- Created searchGlobal function in dataService.

- Refined header UI with an interactive, categorized search results dropdown.

services/dataService.ts

@@ -17,6 +17,19 @@ const getHeaders = () => {
   };
 };
 
+export const searchGlobal = async (query: string): Promise<{ members: User[], teams: any[], attendances: any[] }> => {
+  try {
+    const response = await fetch(`${API_URL}/search?q=${encodeURIComponent(query)}`, {
+      headers: getHeaders()
+    });
+    if (!response.ok) throw new Error('Search failed');
+    return await response.json();
+  } catch (error) {
+    console.error("API Error (searchGlobal):", error);
+    return { members: [], teams: [], attendances: [] };
+  }
+};
+
 export const getAttendances = async (tenantId: string, filter: DashboardFilter): Promise<Attendance[]> => {
   try {
     const params = new URLSearchParams();