* Implement Docker QEMU multi-arch wheel building system

This introduces a comprehensive Docker-based build system that solves
ABI compatibility issues and ARM64 runner availability problems using
QEMU emulation for precise cross-platform wheel generation.

## New Components

### Dockerfile.wheels
- Multi-stage build supporting Debian 12, Rocky Linux 9, Ubuntu 24.04
- Installs complete toolchain: just, uv, rust, build dependencies
- Builds wheels for all Python versions via 'just build-all'
- Generates build metadata with glibc/musl version info
- Supports AMD64 and ARM64 architectures via QEMU

### Docker Bake Configuration (docker-bake.hcl)
- Orchestrates multi-platform builds
- GitHub Actions cache integration
- Local development targets for testing

### GitHub Actions Workflow (wheels-docker.yml)
- Matrix builds across 6 target environments (3 OS × 2 arch)
- QEMU emulation for ARM64 builds (no runner dependency)
- Publishes to GitHub Releases and PyPI
- Comprehensive build metadata and wheel inventory

### Testing Infrastructure
- test-docker-builds.sh: Local testing script
- docs/DOCKER_BUILDS.md: Complete documentation
- Wheel installation validation

## Benefits

- **ABI Control**: Precise glibc targeting per distribution
- **ARM64 Support**: No GitHub runner availability issues
- **Customer Alignment**: Rocky Linux 9 wheels for RHEL environments
- **Reproducible**: Identical Docker environments
- **Fast**: Parallel builds, Docker layer caching

## Target Environments

- Debian 12 (glibc 2.36): Modern systems, containers
- Rocky Linux 9 (glibc 2.34): Enterprise RHEL environments
- Ubuntu 24.04 (glibc 2.39): Latest Ubuntu LTS

This replaces the previous native GitHub Actions builds with a more
reliable, controllable, and comprehensive wheel building system.

* Simplify Docker workflow to use native container syntax

- Remove complex Docker Buildx bake actions
- Use GitHub Actions native container: field instead
- Install dependencies directly in container steps
- Maintain multi-platform support for Debian 12, Rocky 9, Ubuntu 24.04

* Fix Rocky Linux curl-minimal conflict in Docker workflow

Add --allowerasing flag to dnf install to resolve conflict between
curl-minimal (pre-installed) and curl package in Rocky Linux 9 containers.

* Add build metadata generation and fix upload warnings

- Generate dist/build-info.txt with system and build tool information
- Add if-no-files-found: ignore to prevent upload warnings
- Include build date, container info, glibc version, and tool versions