feat(cache): add pingora-cache integration with per-route config

Add in-memory HTTP response cache using pingora-cache MemCache backend.
Cache runs after the detection pipeline so cache hits bypass upstream
request modifications and body rewriting. Respects Cache-Control
(no-store, private, s-maxage, max-age), skips caching for routes with
body rewrites or auth subrequest headers, and supports configurable
default TTL, stale-while-revalidate, and max file size per route.

Signed-off-by: Sienna Meridian Satterwhite <sienna@sunbeam.pt>

tests/e2e.rs

@@ -104,6 +104,7 @@ fn start_proxy_once(backend_port: u16) {
             rewrites: vec![],
             body_rewrites: vec![],
             response_headers: vec![],
+            cache: None,
         }];
         let acme_routes: AcmeRoutes = Arc::new(RwLock::new(HashMap::new()));
         let compiled_rewrites = SunbeamProxy::compile_rewrites(&routes);

tests/scanner_test.rs

@@ -18,6 +18,7 @@ fn test_routes() -> Vec<RouteConfig> {
             rewrites: vec![],
             body_rewrites: vec![],
             response_headers: vec![],
+            cache: None,
         },
         RouteConfig {
             host_prefix: "api".into(),
@@ -30,6 +31,7 @@ fn test_routes() -> Vec<RouteConfig> {
             rewrites: vec![],
             body_rewrites: vec![],
             response_headers: vec![],
+            cache: None,
         },
     ]
 }