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>
Add a prometheus metrics module with counters for requests, DDoS/scanner/
rate-limit decisions, active connections gauge, and request duration
histogram. Spawn a lightweight HTTP server on a configurable port
(default 9090) serving /metrics and /health endpoints.
Signed-off-by: Sienna Meridian Satterwhite <sienna@sunbeam.pt>
