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/pages/Tracker.jsx

@@ -0,0 +1,52 @@
+import { useState, lazy, Suspense } from "react"
+import Navigation from "../components/Navigation"
+
+// Import pages as components (they render their own content but we strip their Navigation)
+import HabitsContent from "./Habits"
+import TasksContent from "./Tasks"
+import StatsContent from "./Stats"
+
+const tabs = [
+  { key: "habits", label: "Привычки", icon: "🎯" },
+  { key: "tasks", label: "Задачи", icon: "✅" },
+  { key: "stats", label: "Статистика", icon: "📊" },
+]
+
+export default function Tracker() {
+  const [activeTab, setActiveTab] = useState("habits")
+
+  return (
+    <div className="min-h-screen bg-surface-50 dark:bg-gray-950 gradient-mesh pb-24">
+      <header className="bg-white/70 dark:bg-gray-900/70 backdrop-blur-xl border-b border-gray-100/50 dark:border-gray-800 sticky top-0 z-10">
+        <div className="max-w-lg mx-auto px-4 py-4">
+          <h1 className="text-xl font-display font-bold text-gray-900 dark:text-white">
+            📊 Трекер
+          </h1>
+        </div>
+        <div className="max-w-lg mx-auto px-4 pb-3 flex gap-2">
+          {tabs.map((t) => (
+            <button
+              key={t.key}
+              onClick={() => setActiveTab(t.key)}
+              className={`flex-1 py-2 rounded-xl text-sm font-semibold transition ${
+                activeTab === t.key
+                  ? "bg-primary-500 text-white"
+                  : "bg-gray-100 dark:bg-gray-800 text-gray-600 dark:text-gray-400"
+              }`}
+            >
+              {t.icon} {t.label}
+            </button>
+          ))}
+        </div>
+      </header>
+
+      <div>
+        {activeTab === "habits" && <HabitsContent embedded />}
+        {activeTab === "tasks" && <TasksContent embedded />}
+        {activeTab === "stats" && <StatsContent embedded />}
+      </div>
+
+      <Navigation />
+    </div>
+  )
+}