Add frontend spec

frontend/spec/pages/relay-edit.md

@@ -0,0 +1,21 @@
+# Relay Edit
+
+The relay edit page lets an authenticated tenant update relay metadata and returns to relay detail on success.
+
+```pug
+page(path="/relays/:id/edit", auth="required", shell="app")
+  back_link(href="/relays/:id", label="Back")
+  header
+    title Edit Relay
+
+  loading_state(message="Loading relay...")
+  error_state(message="Failed to load relay.")
+
+  form(action="update_tenant_relay")
+    field(name="name", label="Relay Name", required=true)
+    field(name="subdomain", label="Subdomain", required=true)
+    field(name="icon", label="Icon URL", type="url")
+    field(name="description", label="Description", type="textarea")
+    submit_button(default="Save Changes", loading="Saving...")
+    error_message(on="submit_failure")
+```