Add Prettier for TypeScript formatting

- Install prettier
- Configure .prettierrc.json and .prettierignore
- Add npm scripts: format, format:check
- Add Makefile target: format-frontend
- Format all frontend files

frontend/app/page.test.tsx

@@ -19,12 +19,10 @@ let mockUser: { id: number; email: string; roles: string[]; permissions: string[
 };
 let mockIsLoading = false;
 const mockLogout = vi.fn();
-const mockHasPermission = vi.fn((permission: string) => 
-  mockUser?.permissions.includes(permission) ?? false
-);
-const mockHasRole = vi.fn((role: string) => 
-  mockUser?.roles.includes(role) ?? false
+const mockHasPermission = vi.fn(
+  (permission: string) => mockUser?.permissions.includes(permission) ?? false
 );
+const mockHasRole = vi.fn((role: string) => mockUser?.roles.includes(role) ?? false);
 
 vi.mock("./auth-context", () => ({
   useAuth: () => ({
@@ -52,12 +50,10 @@ beforeEach(() => {
     permissions: ["view_counter", "increment_counter", "use_sum"],
   };
   mockIsLoading = false;
-  mockHasPermission.mockImplementation((permission: string) =>
-    mockUser?.permissions.includes(permission) ?? false
-  );
-  mockHasRole.mockImplementation((role: string) =>
-    mockUser?.roles.includes(role) ?? false
+  mockHasPermission.mockImplementation(
+    (permission: string) => mockUser?.permissions.includes(permission) ?? false
   );
+  mockHasRole.mockImplementation((role: string) => mockUser?.roles.includes(role) ?? false);
 });
 
 afterEach(() => {
@@ -101,7 +97,7 @@ describe("Home - Authenticated", () => {
 
     render(<Home />);
     fireEvent.click(screen.getByText("Sign out"));
-    
+
     await waitFor(() => {
       expect(mockLogout).toHaveBeenCalled();
       expect(mockPush).toHaveBeenCalledWith("/login");
@@ -238,7 +234,7 @@ describe("Home - Navigation", () => {
     } as Response);
 
     render(<Home />);
-    
+
     await waitFor(() => {
       expect(screen.getByText("My Profile")).toBeDefined();
     });
@@ -257,7 +253,7 @@ describe("Home - Navigation", () => {
     } as Response);
 
     render(<Home />);
-    
+
     // Wait for render - admin sees admin nav (Audit, Invites) not regular nav
     await waitFor(() => {
       expect(screen.getByText("Audit")).toBeDefined();