Serve Kura’s HTTP cache and REAPI gRPC on a single co-hosted listener

Kura’s HTTP cache API and REAPI gRPC surface are now served from a single co-hosted listener dispatched by path, instead of two separate ports (e.g. 4000 and 50051). This unblocks tuist bazel setup against a runner that only knows a single TUIST_CACHE_ENDPOINT URL, which previously landed on the HTTP listener when generating its REAPI target and failed with “Unexpected non-200 HTTP Status Code”. Public CLI/Bazel users keep their existing dial addresses (same host, same TLS, same :443). Self-hosters upgrading from kura 0.10.15 or earlier must drop KURA_GRPC_PORT / KURA_GRPC_TLS_* and point gRPC clients at the cache port, 4000 by default, optionally KURA_HTTPS_PORT (default 4443) when TLS cert/key env vars are set.