feat: add new subscription tier and update credit configurations

- Introduced a new "max" subscription tier with associated monthly credits and top-up limits.
- Updated existing subscription tiers' monthly credits and top-up limits for "starter", "pro", and "business".
- Enhanced credit display and overview components to reflect the new tier and its attributes.
- Integrated Polar authentication features for improved subscription management and credit handling.

app/(app)/settings/billing/page.tsx

@@ -0,0 +1,29 @@
+import { ManageSubscription } from "@/components/billing/manage-subscription";
+import { PricingCards } from "@/components/billing/pricing-cards";
+import { TopupPanel } from "@/components/billing/topup-panel";
+
+export default function BillingPage() {
+  return (
+    <div className="mx-auto max-w-5xl space-y-10 p-6">
+      <div>
+        <h1 className="text-2xl font-semibold">Billing</h1>
+        <p className="mt-1 text-muted-foreground">Manage your plan and credits</p>
+      </div>
+
+      <section className="space-y-4">
+        <h2 className="text-lg font-medium">Current plan</h2>
+        <ManageSubscription />
+      </section>
+
+      <section className="space-y-4">
+        <h2 className="text-lg font-medium">Change plan</h2>
+        <PricingCards />
+      </section>
+
+      <section className="space-y-4">
+        <h2 className="text-lg font-medium">Buy credits</h2>
+        <TopupPanel />
+      </section>
+    </div>
+  );
+}