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/components/general-settings-panel.tsx

@@ -0,0 +1,75 @@
+import { useQuery } from "@tanstack/react-query"
+import { CircleCheck, CircleX, Loader2 } from "lucide-react"
+
+import { getServerUrl } from "@/lib/server-url"
+
+import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card"
+
+async function checkHealth(serverUrl: string): Promise<boolean> {
+  const res = await fetch(`${serverUrl}/health`)
+  if (!res.ok) throw new Error(`HTTP ${res.status}`)
+  const data = (await res.json()) as { status: string }
+  if (data.status !== "ok") throw new Error("Unexpected response")
+  return true
+}
+
+export function GeneralSettingsPanel() {
+  const serverUrl = getServerUrl()
+
+  const { isLoading, isError, error } = useQuery({
+    queryKey: ["health", serverUrl],
+    queryFn: () => checkHealth(serverUrl),
+  })
+
+  const status = isLoading ? "checking" : isError ? "error" : "ok"
+  const errorMsg = error instanceof Error ? error.message : null
+
+  return (
+    <div className="mx-auto max-w-xl space-y-6">
+      <div className="space-y-1">
+        <h2 className="text-lg font-semibold tracking-tight">General</h2>
+        <p className="text-sm text-muted-foreground">
+          Backend server information.
+        </p>
+      </div>
+
+      <Card className="-mx-4">
+        <CardHeader className="pb-4">
+          <CardTitle className="text-sm">Server</CardTitle>
+          <CardDescription>
+            Connected backend instance.
+          </CardDescription>
+        </CardHeader>
+        <CardContent>
+          <div className="space-y-3 text-sm">
+            <div className="flex items-center justify-between gap-4">
+              <span className="shrink-0 text-muted-foreground">URL</span>
+              <span className="select-text truncate font-mono text-xs">{serverUrl}</span>
+            </div>
+            <div className="flex items-center justify-between">
+              <span className="text-muted-foreground">Status</span>
+              {status === "checking" && (
+                <span className="flex items-center gap-1.5 text-xs text-muted-foreground">
+                  <Loader2 className="size-3 animate-spin" />
+                  Checking…
+                </span>
+              )}
+              {status === "ok" && (
+                <span className="flex items-center gap-1.5 text-xs text-muted-foreground">
+                  <CircleCheck className="size-3.5 text-primary" />
+                  Connected
+                </span>
+              )}
+              {status === "error" && (
+                <span className="flex items-center gap-1.5 text-xs text-destructive">
+                  <CircleX className="size-3.5" />
+                  {errorMsg ?? "Unreachable"}
+                </span>
+              )}
+            </div>
+          </div>
+        </CardContent>
+      </Card>
+    </div>
+  )
+}