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

.env.example

@@ -5,8 +5,28 @@ AUTH_SECRET=replace-me
 DATABASE_URL=postgres://user:pass@host:5432/db
 
 # EGBE LiteLLM proxy — auto-injected by app-deploy.sh from the deploying instance
-EGBE_AI_API_URL=https://proxy.gcp.egbe.dev/v1
+EGBE_AI_API_URL=https://litellm.gcp.egbe.dev
 EGBE_AI_API_KEY=
 
 # Public origin of this app — auto-injected by app-deploy.sh
 NEXT_PUBLIC_BASE_URL=http://localhost:3000
+
+# --- analytics (umami) ---
+# Auto-injected by app-deploy.sh after `analytics-site-create.sh <slug> <host> "<Name>"`
+NEXT_PUBLIC_UMAMI_SCRIPT_URL=
+NEXT_PUBLIC_UMAMI_WEBSITE_ID=
+
+# --- billing (payment gateway) ---
+# Auto-injected by app-deploy.sh from the deploying instance
+EGBE_PAYMENT_GATEWAY_URL=https://payments.gcp.egbe.dev
+EGBE_GATEWAYS_TOKEN=
+EGBE_PAYMENT_GATEWAY_WEBHOOK_SECRET=
+EGBE_PAYMENT_GATEWAY_WEBHOOK_HEADER=x-egbe-payment-signature
+
+# Stripe price ID for the Pro plan — set per-product after creating the product via
+# the payment gateway API. Without it the upgrade button returns 501.
+PRO_STRIPE_PRICE_ID=
+
+# App slug used in the webhook URL when creating checkout sessions. Must match the
+# slug you passed to app-deploy.sh.
+APP_SLUG=chatbot