feat: unified navigation hub + categories tab + mobile scroll fix

- Navigation: 4 items (Home, Tracker, Finance, Settings)
- Tracker page: tabs for Habits, Tasks, Stats
- Finance: added Categories tab (CRUD)
- AddTransactionModal: fixed mobile scroll with sticky button
- Home: added finance balance widget
- Legacy routes (/habits, /tasks, /stats) redirect to /tracker

src/App.jsx

@@ -13,6 +13,7 @@ import ForgotPassword from "./pages/ForgotPassword"
 import Stats from "./pages/Stats"
 import Settings from "./pages/Settings"
 import Finance from "./pages/Finance"
+import Tracker from "./pages/Tracker"
 
 function ProtectedRoute({ children }) {
   const { isAuthenticated, isLoading } = useAuthStore()
@@ -93,11 +94,20 @@ export default function App() {
           </ProtectedRoute>
         }
       />
+      <Route
+        path="/tracker"
+        element={
+          <ProtectedRoute>
+            <Tracker />
+          </ProtectedRoute>
+        }
+      />
+      {/* Legacy routes redirect to tracker */}
       <Route
         path="/habits"
         element={
           <ProtectedRoute>
-            <Habits />
+            <Navigate to="/tracker" replace />
           </ProtectedRoute>
         }
       />
@@ -105,7 +115,15 @@ export default function App() {
         path="/tasks"
         element={
           <ProtectedRoute>
-            <Tasks />
+            <Navigate to="/tracker" replace />
+          </ProtectedRoute>
+        }
+      />
+      <Route
+        path="/stats"
+        element={
+          <ProtectedRoute>
+            <Navigate to="/tracker" replace />
           </ProtectedRoute>
         }
       />
@@ -117,14 +135,6 @@ export default function App() {
           </ProtectedRoute>
         }
       />
-      <Route
-        path="/stats"
-        element={
-          <ProtectedRoute>
-            <Stats />
-          </ProtectedRoute>
-        }
-      />
       <Route
         path="/finance"
         element={