Add Umami analytics, subscription tiers, tool-call metering

- Analytics: <Analytics /> in root layout loads umami when NEXT_PUBLIC_UMAMI_* env are set
- Subscription: free/pro tiers in Postgres, daily quotas (10msg/5tool free, 1000/500 pro)
- Chat route: checkAndConsume(chat_message) gate before streamText, 429 when exhausted
- Tool metering: getWeather wrapped with withLimit decorator that deducts tool_call quota
- Pricing page at /pricing with upgrade button
- /api/billing/checkout posts to EGBE payment gateway, /api/billing/webhook verifies HMAC and upgrades user on checkout.session.completed
- UsageBadge in chat header polls /api/usage every 15s
- Dropped now-unused entitlements.ts

app/pricing/page.tsx

@@ -0,0 +1,96 @@
+import { redirect } from "next/navigation";
+import { auth } from "@/app/(auth)/auth";
+import { PricingClient } from "@/components/pricing-client";
+import { LIMITS, type Tier } from "@/lib/subscription/config";
+import { ensureSubscription } from "@/lib/subscription/service";
+
+export const dynamic = "force-dynamic";
+
+export default async function PricingPage({
+  searchParams,
+}: {
+  searchParams: Promise<{ upgraded?: string; canceled?: string }>;
+}) {
+  const session = await auth();
+  if (!session?.user) {
+    redirect("/api/auth/guest?redirectUrl=%2Fpricing");
+  }
+
+  const sub = await ensureSubscription(session.user.id);
+  const params = await searchParams;
+
+  return (
+    <div className="mx-auto flex min-h-dvh max-w-5xl flex-col gap-8 px-6 py-12">
+      <div className="flex flex-col gap-2">
+        <a className="text-muted-foreground text-sm hover:text-foreground" href="/">
+          ← Back to chat
+        </a>
+        <h1 className="font-semibold text-3xl">Pricing</h1>
+        <p className="text-muted-foreground text-sm">
+          You are currently on the <strong>{sub.tier}</strong> tier.
+          {params.upgraded === "1" && (
+            <span className="ml-2 text-green-600">
+              Welcome to Pro — limits updated.
+            </span>
+          )}
+          {params.canceled === "1" && (
+            <span className="ml-2 text-amber-600">Checkout canceled.</span>
+          )}
+        </p>
+      </div>
+
+      <div className="grid gap-4 md:grid-cols-2">
+        <Plan
+          currentTier={sub.tier as Tier}
+          description="Try the chatbot with a small daily quota."
+          price="Free"
+          tier="free"
+        />
+        <Plan
+          currentTier={sub.tier as Tier}
+          description="Higher daily quotas for serious use."
+          price="$10 / month"
+          tier="pro"
+        />
+      </div>
+
+      <PricingClient currentTier={sub.tier as Tier} />
+    </div>
+  );
+}
+
+function Plan({
+  tier,
+  price,
+  description,
+  currentTier,
+}: {
+  tier: Tier;
+  price: string;
+  description: string;
+  currentTier: Tier;
+}) {
+  const tierLimits = LIMITS[tier];
+  const isCurrent = tier === currentTier;
+  return (
+    <div className="flex flex-col gap-4 rounded-2xl border border-border/40 bg-card p-6 shadow-sm">
+      <div>
+        <div className="flex items-baseline justify-between">
+          <div className="font-medium text-lg capitalize">{tier}</div>
+          {isCurrent && (
+            <span className="rounded-full bg-muted px-2 py-0.5 text-muted-foreground text-xs">
+              Current
+            </span>
+          )}
+        </div>
+        <div className="font-semibold text-2xl">{price}</div>
+        <p className="mt-1 text-muted-foreground text-sm">{description}</p>
+      </div>
+      <ul className="flex flex-col gap-1.5 text-sm">
+        <li>• {tierLimits.chat_message} messages / day</li>
+        <li>• {tierLimits.tool_call} tool calls / day</li>
+        <li>• All available models</li>
+      </ul>
+    </div>
+  );
+}