feat: migrate m3-atlas from MinIO to RustFS

- Replace minio.nix with rustfs.nix using rustfs-flake NixOS module
- Add rustfs flake input (github:rustfs/rustfs-flake)
- Reuse same ports (API: 3008, Console: 3007) and data dir (/var/storage/s3)
- Add separate agenix secrets for access-key and secret-key
- Keep Traefik routes unchanged (s3.m3tam3re.com, minio.m3tam3re.com)
- MinIO had 6 unfixed CVEs and is abandoned upstream

hosts/m3-atlas/services/default.nix

@@ -4,7 +4,7 @@
     ./containers
     ./gitea.nix
     ./gitea-actions-runner.nix
-    ./minio.nix
+    ./rustfs.nix
     ./mysql.nix
     ./netbird.nix
     ./n8n.nix