feat: Refactor user management to replace email with username across the application

src/app/api/admin/users/[id]/route.js

@@ -78,7 +78,7 @@ async function updateUserHandler(req, { params }) {
 		
 		if (error.message.includes("already exists")) {
 			return NextResponse.json(
-				{ error: "A user with this email already exists" },
+				{ error: "A user with this username already exists" },
 				{ status: 409 }
 			);
 		}

src/app/api/admin/users/route.js

@@ -27,9 +27,9 @@ async function createUserHandler(req) {
 		const data = await req.json();
 		
 		// Validate required fields
-		if (!data.name || !data.email || !data.password) {
+		if (!data.name || !data.username || !data.password) {
 			return NextResponse.json(
-				{ error: "Name, email, and password are required" },
+				{ error: "Name, username, and password are required" },
 				{ status: 400 }
 			);
 		}
@@ -53,7 +53,7 @@ async function createUserHandler(req) {
 
 		const newUser = await createUser({
 			name: data.name,
-			email: data.email,
+			username: data.username,
 			password: data.password,
 			role: data.role || "user",
 			is_active: data.is_active !== undefined ? data.is_active : true
@@ -68,7 +68,7 @@ async function createUserHandler(req) {
 		
 		if (error.message.includes("already exists")) {
 			return NextResponse.json(
-				{ error: "A user with this email already exists" },
+				{ error: "A user with this username already exists" },
 				{ status: 409 }
 			);
 		}