Add riscv64 architecture support for noble and trixie

[igorpecovnik]

Summary

• Add riscv64 builds for Ubuntu noble using ubuntu-24.04-riscv runner
• Add riscv64 builds for Debian trixie using ubuntu-24.04-riscv runner
• Update multi-arch manifests to include riscv64 for both releases

Test plan

• Workflow runs successfully on ubuntu-24.04-riscv runners
• Docker images build correctly for riscv64 architecture
• Multi-arch manifests include all three architectures (amd64, arm64, riscv64)