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/common/src/config/telemetry.rs

@@ -141,7 +141,8 @@ impl Telemetry {
 }
 
 impl Tracers {
-    pub async fn parse(bp: &mut Bootstrap, storage: &Storage) -> Self {
+    // inbuxa: `_storage` is unused until monitoring history (stored traces and metrics) is rebuilt
+    pub async fn parse(bp: &mut Bootstrap, _storage: &Storage) -> Self {
         let mut custom_levels = AHashMap::new();
         let mut tracers: Vec<TelemetrySubscriber> = Vec::new();
         let mut global_interests = Interests::default();