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

components/chat/usage-badge.tsx

@@ -0,0 +1,44 @@
+"use client";
+
+import Link from "next/link";
+import useSWR from "swr";
+import type { QuotaSummary } from "@/lib/subscription/service";
+import { fetcher } from "@/lib/utils";
+
+export function UsageBadge() {
+  const { data } = useSWR<QuotaSummary>(
+    `${process.env.NEXT_PUBLIC_BASE_PATH ?? ""}/api/usage`,
+    fetcher,
+    {
+      refreshInterval: 15_000,
+      revalidateOnFocus: true,
+    }
+  );
+
+  if (!data) {
+    return null;
+  }
+
+  const isPro = data.tier === "pro";
+  const lowQuota =
+    !isPro &&
+    (data.messages.remaining <= 2 || data.toolCalls.remaining <= 1);
+
+  return (
+    <Link
+      className={`flex items-center gap-2 rounded-lg border px-2.5 py-1 text-[11px] font-medium transition-colors ${
+        lowQuota
+          ? "border-amber-500/40 bg-amber-500/10 text-amber-600 hover:bg-amber-500/15"
+          : "border-border/40 text-muted-foreground hover:text-foreground"
+      }`}
+      href="/pricing"
+      title={`${data.tier} tier — ${data.toolCalls.used}/${data.toolCalls.limit} tool calls today`}
+    >
+      <span className="uppercase tracking-wider opacity-60">{data.tier}</span>
+      <span>
+        {data.messages.used}/{data.messages.limit} msgs
+      </span>
+      {isPro ? null : <span aria-hidden>→</span>}
+    </Link>
+  );
+}