Scaffold @forte/admin package with React, Vite, shadcn/ui, TanStack Router

Sets up the admin frontend with login page, auth guard, API client, Zustand
auth store, and all shadcn/ui components. Vite proxies /v1 to backend in dev.

packages/admin/src/hooks/use-mobile.ts

@@ -0,0 +1,19 @@
+import * as React from "react"
+
+const MOBILE_BREAKPOINT = 768
+
+export function useIsMobile() {
+  const [isMobile, setIsMobile] = React.useState<boolean | undefined>(undefined)
+
+  React.useEffect(() => {
+    const mql = window.matchMedia(`(max-width: ${MOBILE_BREAKPOINT - 1}px)`)
+    const onChange = () => {
+      setIsMobile(window.innerWidth < MOBILE_BREAKPOINT)
+    }
+    mql.addEventListener("change", onChange)
+    setIsMobile(window.innerWidth < MOBILE_BREAKPOINT)
+    return () => mql.removeEventListener("change", onChange)
+  }, [])
+
+  return !!isMobile
+}