feat(frontend): Transform layout to use shadcn dashboard-01 with iOS PWA safe area support.

- Replace custom layout with modern SidebarProvider/SidebarInset structure
- Add AppSidebar component using shadcn patterns with preserved account summary
- Add SiteHeader component with SidebarTrigger integration
- Install shadcn sidebar, separator, and related UI components
- Fix iOS PWA safe area issues - sidebar no longer overlaps dynamic island/notch
- Add pt-safe-top and pl-safe-left classes to sidebar and header components
- Remove legacy Sidebar.tsx and Header.tsx components
- Preserve all existing functionality: navigation, API health status, theme toggle, PWA features
- Improve mobile responsive behavior with built-in shadcn drawer patterns

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/src/components/SiteHeader.tsx

@@ -0,0 +1,71 @@
+import { useLocation } from "@tanstack/react-router";
+import { Activity, Wifi, WifiOff } from "lucide-react";
+import { useQuery } from "@tanstack/react-query";
+import { apiClient } from "../lib/api";
+import { ThemeToggle } from "./ui/theme-toggle";
+import { Separator } from "./ui/separator";
+import { SidebarTrigger } from "./ui/sidebar";
+
+const navigation = [
+  { name: "Overview", to: "/" },
+  { name: "Transactions", to: "/transactions" },
+  { name: "Analytics", to: "/analytics" },
+  { name: "Notifications", to: "/notifications" },
+  { name: "Settings", to: "/settings" },
+];
+
+export function SiteHeader() {
+  const location = useLocation();
+  const currentPage =
+    navigation.find((item) => item.to === location.pathname)?.name ||
+    "Dashboard";
+
+  const {
+    data: healthStatus,
+    isLoading: healthLoading,
+    isError: healthError,
+  } = useQuery({
+    queryKey: ["health"],
+    queryFn: apiClient.getHealth,
+    refetchInterval: 30000,
+  });
+
+  return (
+    <header className="flex h-16 shrink-0 items-center gap-2 border-b transition-[width,height] ease-linear pt-safe-top">
+      <div className="flex w-full items-center gap-1 px-4 lg:gap-2 lg:px-6">
+        <SidebarTrigger className="-ml-1" />
+        <Separator
+          orientation="vertical"
+          className="mx-2 data-[orientation=vertical]:h-4"
+        />
+        <h1 className="text-lg font-semibold text-card-foreground">
+          {currentPage}
+        </h1>
+
+        <div className="ml-auto flex items-center space-x-3">
+          <div className="flex items-center space-x-1">
+            {healthLoading ? (
+              <>
+                <Activity className="h-4 w-4 text-muted-foreground animate-pulse" />
+                <span className="text-sm text-muted-foreground">
+                  Checking...
+                </span>
+              </>
+            ) : healthError || healthStatus?.status !== "healthy" ? (
+              <>
+                <WifiOff className="h-4 w-4 text-destructive" />
+                <span className="text-sm text-destructive">Disconnected</span>
+              </>
+            ) : (
+              <>
+                <Wifi className="h-4 w-4 text-green-500" />
+                <span className="text-sm text-muted-foreground">Connected</span>
+              </>
+            )}
+          </div>
+          <ThemeToggle />
+        </div>
+      </div>
+    </header>
+  );
+}