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/(chat)/api/billing/webhook/route.ts

@@ -0,0 +1,99 @@
+import { eq } from "drizzle-orm";
+import { drizzle } from "drizzle-orm/postgres-js";
+import postgres from "postgres";
+import {
+  verifyWebhookSignature,
+  webhookHeaderName,
+} from "@/lib/billing/gateway";
+import { webhookEvent } from "@/lib/db/schema";
+import { cancelSubscription, upgradeToPro } from "@/lib/subscription/service";
+
+const client = postgres(process.env.DATABASE_URL ?? "");
+const db = drizzle(client);
+
+type StripeCheckoutSession = {
+  id: string;
+  payment_status?: string;
+  customer?: string;
+  subscription?: string;
+  metadata?: { userId?: string };
+};
+
+type StripeSubscription = {
+  id: string;
+  customer?: string;
+  current_period_end?: number;
+  metadata?: { userId?: string };
+};
+
+type WebhookEnvelope = {
+  id: string;
+  type: string;
+  data: { object: StripeCheckoutSession | StripeSubscription };
+};
+
+export async function POST(request: Request) {
+  const rawBody = await request.text();
+  const signature = request.headers.get(webhookHeaderName);
+
+  if (!verifyWebhookSignature(rawBody, signature)) {
+    return Response.json({ error: "invalid_signature" }, { status: 401 });
+  }
+
+  let envelope: WebhookEnvelope;
+  try {
+    envelope = JSON.parse(rawBody);
+  } catch {
+    return Response.json({ error: "invalid_json" }, { status: 400 });
+  }
+
+  const existing = await db
+    .select()
+    .from(webhookEvent)
+    .where(eq(webhookEvent.id, envelope.id))
+    .limit(1);
+  if (existing[0]) {
+    return Response.json({ ok: true, dedup: true });
+  }
+
+  try {
+    await handleEvent(envelope);
+  } catch (error) {
+    console.error("webhook handler failed", error);
+    return Response.json({ error: "handler_failed" }, { status: 500 });
+  }
+
+  await db
+    .insert(webhookEvent)
+    .values({ id: envelope.id, type: envelope.type })
+    .onConflictDoNothing();
+
+  return Response.json({ ok: true });
+}
+
+async function handleEvent(envelope: WebhookEnvelope) {
+  switch (envelope.type) {
+    case "checkout.session.completed": {
+      const obj = envelope.data.object as StripeCheckoutSession;
+      const userId = obj.metadata?.userId;
+      if (!userId) {
+        return;
+      }
+      await upgradeToPro(userId, {
+        stripeCustomerId: obj.customer,
+        stripeSubscriptionId: obj.subscription,
+      });
+      return;
+    }
+    case "customer.subscription.deleted": {
+      const obj = envelope.data.object as StripeSubscription;
+      const userId = obj.metadata?.userId;
+      if (!userId) {
+        return;
+      }
+      await cancelSubscription(userId);
+      return;
+    }
+    default:
+  }
+}