Redesign login as landing page, remove self-registration, add nav+placeholders

- LoginPage: centred landing layout with logo placeholder box and business
  name headline (BUSINESS_NAME constant); registration link removed
- useAuth: post-login redirect goes to / (dashboard) directly
- Nav: Home | Apps | Settings | Logout (consistent on all protected pages)
- AppsPage, SettingsPage: white placeholder pages with headline
- App.tsx: /apps and /settings private routes; removed /register,
  /register-success, /login-success; catch-all → /
- Deleted: RegisterPage, RegisterSuccessPage, LoginSuccessPage
- Backend /api/auth/register kept for future admin-side user creation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -1,11 +1,10 @@
 import { Routes, Route, Navigate } from "react-router-dom";
+import { useAuth } from "./hooks/useAuth";
 import LoginPage from "./pages/LoginPage";
-import RegisterPage from "./pages/RegisterPage";
 import DashboardPage from "./pages/DashboardPage";
 import ProfilePage from "./pages/ProfilePage";
-import LoginSuccessPage from "./pages/LoginSuccessPage";
-import RegisterSuccessPage from "./pages/RegisterSuccessPage";
-import { useAuth } from "./hooks/useAuth";
+import AppsPage from "./pages/AppsPage";
+import SettingsPage from "./pages/SettingsPage";
 
 function PrivateRoute({ children }: { children: React.ReactNode }) {
   const { token } = useAuth();
@@ -16,32 +15,14 @@ export default function App() {
   return (
     <Routes>
       <Route path="/login" element={<LoginPage />} />
-      <Route path="/register" element={<RegisterPage />} />
-      <Route path="/register-success" element={<RegisterSuccessPage />} />
-      <Route
-        path="/login-success"
-        element={
-          <PrivateRoute>
-            <LoginSuccessPage />
-          </PrivateRoute>
-        }
-      />
-      <Route
-        path="/"
-        element={
-          <PrivateRoute>
-            <DashboardPage />
-          </PrivateRoute>
-        }
-      />
-      <Route
-        path="/profile"
-        element={
-          <PrivateRoute>
-            <ProfilePage />
-          </PrivateRoute>
-        }
-      />
+
+      <Route path="/" element={<PrivateRoute><DashboardPage /></PrivateRoute>} />
+      <Route path="/apps" element={<PrivateRoute><AppsPage /></PrivateRoute>} />
+      <Route path="/settings" element={<PrivateRoute><SettingsPage /></PrivateRoute>} />
+      <Route path="/profile" element={<PrivateRoute><ProfilePage /></PrivateRoute>} />
+
+      {/* Catch-all */}
+      <Route path="*" element={<Navigate to="/" replace />} />
     </Routes>
   );
 }