feat(admin): add registration policy settings and disabled register state

apps/admin/src/messages/en.json

@@ -13,12 +13,14 @@
     "titles": {
       "signIn": "Sign in to CMS Admin",
       "signUpOwner": "Welcome to CMS Admin",
-      "signUpUser": "Create an admin account"
+      "signUpUser": "Create an admin account",
+      "signUpDisabled": "Registration is disabled"
     },
     "descriptions": {
       "signIn": "Better Auth is active on this app via /api/auth.",
       "signUpOwner": "Create the first owner account to initialize this admin instance.",
-      "signUpUser": "Self-registration is enabled for admin users."
+      "signUpUser": "Self-registration is enabled for admin users.",
+      "signUpDisabled": "Self-registration is currently turned off by an administrator."
     },
     "fields": {
       "name": "Name",
@@ -42,7 +44,8 @@
     },
     "messages": {
       "ownerCreated": "Owner account created. Registration is now disabled.",
-      "accountCreated": "Account created."
+      "accountCreated": "Account created.",
+      "registrationDisabled": "Registration is disabled for this admin instance. Ask an administrator to create an account or enable self-registration."
     },
     "errors": {
       "nameRequired": "Name is required for account creation",
@@ -52,6 +55,33 @@
       "networkSignUp": "Network error while signing up"
     }
   },
+  "settings": {
+    "badge": "Admin Settings",
+    "title": "Settings",
+    "description": "Manage runtime policies for the admin authentication and onboarding flow.",
+    "actions": {
+      "backToDashboard": "Back to dashboard"
+    },
+    "registration": {
+      "title": "Admin self-registration",
+      "description": "When enabled, /register can create additional admin accounts after initial owner bootstrap.",
+      "currentStatusLabel": "Current status",
+      "status": {
+        "enabled": "Enabled",
+        "disabled": "Disabled"
+      },
+      "checkboxLabel": "Allow self-registration on /register for admin users",
+      "actions": {
+        "save": "Save registration policy"
+      },
+      "success": {
+        "updated": "Registration policy updated."
+      },
+      "errors": {
+        "updateFailed": "Saving settings failed. Ensure database migrations are applied."
+      }
+    }
+  },
   "dashboard": {
     "badge": "Admin App",
     "title": "Content Dashboard",