ci(cache): Migrate Rust cache to runner-managed multi-level Redis and S3

Centralize cache service management in the Gitea runner for improved persistence and reliability using an SSD-backed S3 backend. This ensures robust verification of multi-tier cache operations.

ci/setup-builder.sh

@@ -1,6 +1,5 @@
 #!/bin/sh
 set -eu
-docker compose -p openwrt-rust -f ci/cache.compose.yml up -d --wait
 if ! docker buildx inspect openwrt-sdk-rust >/dev/null 2>&1; then
     docker buildx create --name openwrt-sdk-rust --driver docker-container \
         --driver-opt network=host,memory=20g,memory-swap=20g,cpu-period=100000,cpu-quota=800000 \