refactor: rename materia → beanflows throughout codebase

- Rename src/materia/ → src/beanflows/ (Python package)
- Rename transform/sqlmesh_materia/ → transform/sqlmesh_beanflows/
- Rename infra/supervisor/materia-supervisor.service → beanflows-supervisor.service
- Rename infra/backup/materia-backup.{service,timer} → beanflows-backup.{service,timer}
- Update all path strings: /opt/materia → /opt/beanflows, /data/materia → /data/beanflows
- Update pyproject.toml: project name, CLI entrypoint, workspace source key
- Update all internal imports from materia.* → beanflows.*
- Update infra scripts: REPO_DIR, service names, systemctl references
- Fix docker-compose.prod.yml: /data/materia → /data/beanflows (bind mount path)

Intentionally left unchanged: Pulumi stack name (materia-infrastructure) and
Hetzner resource names ("materia-key", "managed_by: materia") — these reference
live cloud infrastructure and require separate cloud-side renames.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

infra/backup/beanflows-backup.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=Beanflows Landing Data Backup to R2
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/rclone sync /data/beanflows/landing/ r2:backup/beanflows/landing/ --log-level INFO
+TimeoutStartSec=1800