docs: restructure help pages into bundles and add new reference pages

Convert several pages to leaf bundles with WebP screenshots, add
api-keys, domain-availability, notifications, provider-features,
quotas, services, settings, signup and subdomains pages, and refresh
existing content.

content/pages/_index.en.md

@@ -6,4 +6,30 @@ archetype: chapter
 weight: 10
 ---
 
+This section walks through happyDomain feature by feature, following the path a new user
+takes: from creating an account to publishing a fully managed zone.
+
+You start by [creating an account]({{% relref "signup" %}}) and [logging in]({{% relref "login" %}}),
+then land on the [dashboard]({{% relref "domains" %}}) that centralizes all your domains.
+
+Before importing a domain, you connect a [provider]({{% relref "provider-list" %}}): happyDomain
+[adds]({{% relref "provider-new-choice" %}}) and [configures]({{% relref "provider-update" %}})
+it for you, whatever its [specific features]({{% relref "provider-features" %}}).
+
+You can then [import a domain]({{% relref "domain-new" %}}) and explore it in the
+[zone editor]({{% relref "domain-abstract" %}}), which
+lets you manage [subdomains]({{% relref "subdomains" %}}) and group records into
+[services]({{% relref "services" %}}). Every change is reviewed
+before you [publish]({{% relref "publish-changes" %}}) it, and the
+[history]({{% relref "domain-history" %}}) keeps track of everything. You can also
+[import or export]({{% relref "import-export" %}}) the whole zone as a standard file.
+
+happyDomain also helps you keep an eye on your domains with
+[monitoring and checks]({{% relref "checks" %}}), [availability lookups]({{% relref "domain-availability" %}})
+and the [domain test tool]({{% relref "tools-client" %}}).
+
+Finally, you can fine-tune your account: [your account and settings]({{% relref "settings" %}}),
+[sessions and API access]({{% relref "api-keys" %}}),
+[notifications]({{% relref "notifications" %}}) and [quotas]({{% relref "quotas" %}}).
+
 {{% children %}}