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.

crates/aether-data/adapters/postgres/src/pool.rs

@@ -6,17 +6,23 @@ use std::time::Duration;
 
 fn connect_options(config: &PostgresPoolConfig) -> Result<PgConnectOptions, DataLayerError> {
     config.validate()?;
-
-    let ssl_mode = if config.require_ssl {
-        PgSslMode::Require
-    } else {
-        PgSslMode::Prefer
-    };
-
     let options = PgConnectOptions::from_str(config.database_url.trim()).map_err(|err| {
         DataLayerError::InvalidConfiguration(format!("invalid postgres database_url: {err}"))
     })?;
 
+    // Preserve an explicit verification mode from the URL. `require_ssl` is
+    // a minimum transport guarantee, so it may upgrade Disable/Allow/Prefer
+    // to Require but must never silently weaken VerifyCa/VerifyFull.
+    let ssl_mode = if config.require_ssl
+        && !matches!(
+            options.get_ssl_mode(),
+            PgSslMode::VerifyCa | PgSslMode::VerifyFull
+        ) {
+        PgSslMode::Require
+    } else {
+        options.get_ssl_mode()
+    };
+
     Ok(options
         .ssl_mode(ssl_mode)
         .statement_cache_capacity(config.statement_cache_capacity))
@@ -53,8 +59,43 @@ impl PostgresPoolFactory {
 
 #[cfg(test)]
 mod tests {
-    use super::PostgresPoolFactory;
+    use super::{connect_options, PostgresPoolFactory};
     use crate::PostgresPoolConfig;
+    use sqlx::postgres::PgSslMode;
+
+    fn ssl_mode(url: &str, require_ssl: bool) -> PgSslMode {
+        connect_options(&PostgresPoolConfig {
+            database_url: url.to_string(),
+            require_ssl,
+            ..PostgresPoolConfig::default()
+        })
+        .expect("postgres options should parse")
+        .get_ssl_mode()
+    }
+
+    #[test]
+    fn preserves_explicit_postgres_verification_modes() {
+        assert!(matches!(
+            ssl_mode("postgres://localhost/aether?sslmode=verify-full", false),
+            PgSslMode::VerifyFull
+        ));
+        assert!(matches!(
+            ssl_mode("postgres://localhost/aether?sslmode=verify-ca", true),
+            PgSslMode::VerifyCa
+        ));
+    }
+
+    #[test]
+    fn require_ssl_only_upgrades_weak_postgres_modes() {
+        for mode in ["disable", "allow", "prefer"] {
+            let url = format!("postgres://localhost/aether?sslmode={mode}");
+            assert!(matches!(ssl_mode(&url, true), PgSslMode::Require));
+        }
+        assert!(matches!(
+            ssl_mode("postgres://localhost/aether", false),
+            PgSslMode::Prefer
+        ));
+    }
 
     #[tokio::test]
     async fn factory_builds_lazy_pool_from_valid_config() {