Kura now serves HTTP and REAPI gRPC on a single port

The Kura cache now serves both its HTTP cache API and REAPI gRPC surface on the same port (4000 by default for plaintext, 4443 for TLS), instead of requiring separate HTTP and gRPC listeners. This fixes Bazel remote cache setup when only a single cache endpoint is provided, so tuist bazel setup can complete its REAPI handshake and write the .bazelrc.tuist configuration without falling back to a cold cache. Self-hosted deployments should remove the deprecated KURA_GRPC_PORT, KURA_GRPC_TLS_CERT_PATH, and KURA_GRPC_TLS_KEY_PATH settings and point gRPC clients at the cache port.