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-gateway/frontdoor/src/middleware/cf_headers.rs

@@ -1,26 +1,14 @@
 use axum::{extract::Request, middleware::Next, response::Response, Router};
-use http::{header::HeaderName, HeaderMap};
+use http::header::HeaderName;
 
 const CF_EXACT_HEADERS: &[&str] = &["cdn-loop", "true-client-ip"];
 
-#[derive(Clone, Debug)]
-pub struct CfConnectingIp(pub String);
-
 fn should_strip_cf_header(name: &HeaderName) -> bool {
     let normalized = name.as_str();
     normalized.starts_with("cf-") || CF_EXACT_HEADERS.contains(&normalized)
 }
 
-fn cf_connecting_ip(headers: &HeaderMap) -> Option<String> {
-    headers
-        .get("cf-connecting-ip")
-        .and_then(|value| value.to_str().ok())
-        .map(str::trim)
-        .filter(|value| !value.is_empty())
-        .map(|value| value.chars().take(45).collect())
-}
-
-fn strip_cf_headers(headers: &mut HeaderMap) {
+fn strip_cf_headers(headers: &mut http::HeaderMap) {
     let to_remove: Vec<_> = headers
         .keys()
         .filter(|name| should_strip_cf_header(name))
@@ -36,9 +24,6 @@ pub fn apply_cf_header_stripping(router: Router) -> Router {
 }
 
 pub async fn strip_cf_headers_middleware(mut request: Request, next: Next) -> Response {
-    if let Some(client_ip) = cf_connecting_ip(request.headers()) {
-        request.extensions_mut().insert(CfConnectingIp(client_ip));
-    }
     strip_cf_headers(request.headers_mut());
 
     let mut response = next.run(request).await;