- Bump golang:1.24-alpine to golang:1.25-alpine to match go.mod requirement
- Set GOTOOLCHAIN=local to prevent segfault from toolchain download in Docker
This fixes the multiplatform build failure where go mod download would
attempt to download Go 1.25.0 in the container and crash.
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>