feat: add admin dashboard app (#91)

* feat: add admin dashboard app

- React + Vite + TanStack Router + TanStack Query
- Auth with better-auth (login, session, admin guard)
- Source config management (WeatherKit credentials, user config)
- Feed query panel
- Location push card
- General settings with health check
- CORS middleware for cross-origin auth
- Disable CSRF check in dev mode
- Sonner toasts for mutation feedback

Co-authored-by: Ona <no-reply@ona.com>

* fix: use useQuery instead of getQueryData

Co-authored-by: Ona <no-reply@ona.com>

* refactor: remove backend changes from dashboard PR

Backend CORS/CSRF changes moved to #92.
Source registry removed (sources hardcoded in frontend).

Co-authored-by: Ona <no-reply@ona.com>

---------

Co-authored-by: Ona <no-reply@ona.com>

apps/admin-dashboard/src/routes/login.tsx

@@ -0,0 +1,22 @@
+import { createRoute, useNavigate } from "@tanstack/react-router"
+import { useQueryClient } from "@tanstack/react-query"
+
+import type { AuthSession } from "@/lib/auth"
+import { LoginPage } from "@/components/login-page"
+import { Route as rootRoute } from "./__root"
+
+export const Route = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/login",
+  component: function LoginRoute() {
+    const navigate = useNavigate()
+    const queryClient = useQueryClient()
+
+    function handleLogin(session: AuthSession) {
+      queryClient.setQueryData(["session"], session)
+      navigate({ to: "/" })
+    }
+
+    return <LoginPage onLogin={handleLogin} />
+  },
+})