docs: usage quotas

How the instance default, team allowances and user overrides resolve
(including users in several teams), the quota window, who is charged for
agent traffic, how cost budgets price models and what happens to unpriced
ones, and the admin and user API.

docs/content/Deploying/_meta.js

@@ -15,6 +15,10 @@ export default {
     "title": "👥 Access Control & Teams",
     "href": "/Deploying/Access-Control"
   },
+  "Usage-Quotas": {
+    "title": "📊 Usage Quotas",
+    "href": "/Deploying/Usage-Quotas"
+  },
   "Docker-Deploying": {
     "title": "🛳️ Docker Setup",
     "href": "/Deploying/Docker-Deploying"