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>

src/scanner/detector.rs

@@ -166,6 +166,7 @@ mod tests {
             rewrites: vec![],
             body_rewrites: vec![],
             response_headers: vec![],
+            cache: None,
         }];
         ScannerDetector::new(&model, &routes)
     }