Quick fixes from the first boot: recovery admin, upsell, warnings

- The recovery administrator (INBUXA_RECOVERY_ADMIN, or STALWART_RECOVERY_ADMIN)
  is honored only in bootstrap and recovery mode. On a configured server it's
  ignored with a startup warning. Before, it was a standing full-admin login
  for as long as the variable stayed set.
- The Enterprise upsell error is replaced by "This feature isn't available in
  INBUXA yet" for the features still to be rebuilt.
- Workspace warnings: 25 to 0. cargo fix removed the unused imports. The
  seven places where Enterprise code used to plug in keep their parameters,
  each with an inbuxa: comment naming the rebuild that uses it again. The
  antispam test's mock-server imports are back behind pending-rebuild.

crates/store/src/build/registry.rs

@@ -18,7 +18,21 @@ impl RegistryStore {
 
         // Build store
         inner.store = match inner.read_data_store().await {
-            RegistryInit::Ok(data_store) => Store::build(data_store).await?,
+            RegistryInit::Ok(data_store) => {
+                // The recovery administrator exists for first-boot setup and
+                // for recovery mode. On a configured server running normally
+                // it would be a standing full-admin login for whoever knows the
+                // variable, so it's ignored there, and loudly.
+                if !inner.env_recovery_mode && inner.env_recovery_admin.take().is_some() {
+                    eprintln!();
+                    eprintln!("⚠️  INBUXA_RECOVERY_ADMIN (or STALWART_RECOVERY_ADMIN) is set, but the");
+                    eprintln!("   server is configured and not in recovery mode, so it is ignored.");
+                    eprintln!("   Remove it from the environment. To use it for recovery, also set");
+                    eprintln!("   INBUXA_RECOVERY_MODE=1.");
+                    eprintln!();
+                }
+                Store::build(data_store).await?
+            }
             RegistryInit::Err(err) => return Err(err),
             RegistryInit::Bootstrap => {
                 inner.env_recovery_mode = true;