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/dispatch/pool_scheduler.rs

@@ -4806,6 +4806,15 @@ mod tests {
             ))
     }
 
+    fn provider_catalog_credential_state() -> AppState {
+        AppState::new()
+            .expect("credential state should build")
+            .with_data_state_for_tests(
+                GatewayDataState::disabled()
+                    .with_encryption_key_for_tests(aether_crypto::DEVELOPMENT_ENCRYPTION_KEY),
+            )
+    }
+
     fn large_pool_fixture(
         key_count: usize,
         provider_config: Option<serde_json::Value>,
@@ -4856,10 +4865,18 @@ mod tests {
         )
         .expect("endpoint transport should build");
 
+        let credential_state = provider_catalog_credential_state();
         let mut keys = Vec::with_capacity(key_count);
         let mut rows = Vec::with_capacity(key_count);
         for index in 0..key_count {
             let key_id = format!("key-{index:05}");
+            let encrypted_api_key = credential_state
+                .seal_provider_catalog_key_api_key(
+                    "provider-pool",
+                    &key_id,
+                    &format!("secret-{index}"),
+                )
+                .expect("api key should encrypt");
             let mut key = StoredProviderCatalogKey::new(
                 key_id.clone(),
                 "provider-pool".to_string(),
@@ -4871,7 +4888,7 @@ mod tests {
             .expect("key should build")
             .with_transport_fields(
                 Some(json!(["openai:chat"])),
-                Some(format!("secret-{index}")),
+                encrypted_api_key,
                 None,
                 None,
                 None,
@@ -5007,6 +5024,9 @@ mod tests {
     }
 
     fn sample_codex_pool_key(provider_id: &str, key_id: &str) -> StoredProviderCatalogKey {
+        let encrypted_api_key = provider_catalog_credential_state()
+            .seal_provider_catalog_key_api_key(provider_id, key_id, &format!("secret-{key_id}"))
+            .expect("api key should encrypt");
         let mut key = StoredProviderCatalogKey::new(
             key_id.to_string(),
             provider_id.to_string(),
@@ -5018,7 +5038,7 @@ mod tests {
         .expect("key should build")
         .with_transport_fields(
             Some(json!(["openai:responses"])),
-            Some(format!("secret-{key_id}")),
+            encrypted_api_key,
             None,
             None,
             Some(json!({"openai:responses": 1})),