feat(security): harden gateway boundaries and usage policies

Consolidate subscription usage policy enforcement, privacy-safe persistence, and gateway security hardening into one reviewable change.

Includes bounded HTTP and execution envelopes, header and protocol guards, DNS and relay validation, authentication and secret projection hardening, secure backup/install paths, and regression coverage.

apps/aether-gateway/src/handlers/admin/provider/query/models/mod.rs

@@ -29,7 +29,7 @@ use crate::handlers::shared::{
     parse_catalog_auth_config_json, provider_key_health_summary,
     provider_key_status_snapshot_payload,
 };
-use crate::model_fetch::ModelFetchRuntimeState;
+use crate::model_fetch::{safe_model_fetch_error, ModelFetchRuntimeState};
 use crate::provider_key_auth::{
     provider_key_auth_semantics, provider_key_configured_api_formats,
     provider_key_inherits_provider_api_formats,
@@ -319,6 +319,15 @@ fn provider_query_codex_preset_fallback(
     })
 }
 
+fn provider_query_project_model_fetch_errors(
+    errors: impl IntoIterator<Item = String>,
+) -> Vec<String> {
+    errors
+        .into_iter()
+        .map(|error| safe_model_fetch_error(&error))
+        .collect()
+}
+
 async fn provider_query_persist_preset_models(
     state: &AdminAppState<'_>,
     provider: &StoredProviderCatalogProvider,
@@ -564,7 +573,7 @@ async fn provider_query_fetch_models_for_key(
     let outcome = match fetch_models_from_transports(state.app(), &transports).await {
         Ok(outcome) => outcome,
         Err(err) => {
-            all_errors.push(err);
+            all_errors.extend(provider_query_project_model_fetch_errors([err]));
             if let Some(fallback) =
                 provider_query_codex_preset_fallback(provider, &all_errors.join("; "))
             {
@@ -582,7 +591,7 @@ async fn provider_query_fetch_models_for_key(
         }
     };
 
-    all_errors.extend(outcome.errors);
+    all_errors.extend(provider_query_project_model_fetch_errors(outcome.errors));
     let unique_models = outcome.legacy_models;
     if outcome.has_success && !unique_models.is_empty() {
         <AppState as ModelFetchRuntimeState>::write_upstream_models_cache(
@@ -1026,4 +1035,32 @@ mod tests {
             json!(true)
         );
     }
+
+    #[test]
+    fn provider_query_projects_transport_errors_before_exposing_them() {
+        let projected = provider_query_project_model_fetch_errors(vec![
+            "HTTP 401 response body: Authorization: Bearer upstream-secret".to_string(),
+            "connection failed for https://user:[email protected]/v1/models?key=secret"
+                .to_string(),
+        ]);
+
+        assert_eq!(
+            projected,
+            [
+                "Upstream models fetch authentication failed (status 401)",
+                "Upstream models fetch connection failed",
+            ]
+        );
+        let exposed = projected.join("; ");
+        for secret in [
+            "upstream-secret",
+            "Bearer",
+            "user",
+            "password",
+            "example.test",
+            "?key=secret",
+        ] {
+            assert!(!exposed.contains(secret));
+        }
+    }
 }