refactor: migrate to src/ package + add DinD-based E2E runner with debug artifacts

- Replace legacy standalone scripts with a proper src-layout Python package
  (baudolo backup/restore/configure entrypoints via pyproject.toml)
- Remove old scripts/files (backup-docker-to-local.py, recover-docker-from-local.sh,
  databases.csv.tpl, Todo.md)
- Add Dockerfile to build the project image for local/E2E usage
- Update Makefile: build image and run E2E via external runner script
- Add scripts/test-e2e.sh:
  - start DinD + dedicated network
  - recreate DinD data volume (and shared /tmp volume)
  - pre-pull helper images (alpine-rsync, alpine)
  - load local baudolo:local image into DinD
  - run unittest E2E suite inside DinD and abort on first failure
  - on failure: dump host+DinD diagnostics and archive shared /tmp into artifacts/
- Add artifacts/ debug outputs produced by failing E2E runs (logs, events, tmp archive)

https://chatgpt.com/share/694ec23f-0794-800f-9a59-8365bc80f435

src/baudolo/backup/volume.py

@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+import os
+import pathlib
+
+from .shell import BackupException, execute_shell_command
+
+
+def get_storage_path(volume_name: str) -> str:
+    path = execute_shell_command(
+        f"docker volume inspect --format '{{{{ .Mountpoint }}}}' {volume_name}"
+    )[0]
+    return f"{path}/"
+
+
+def get_last_backup_dir(versions_dir: str, volume_name: str, current_backup_dir: str) -> str | None:
+    versions = sorted(os.listdir(versions_dir), reverse=True)
+    for version in versions:
+        candidate = os.path.join(versions_dir, version, volume_name, "files", "")
+        if candidate != current_backup_dir and os.path.isdir(candidate):
+            return candidate
+    return None
+
+
+def backup_volume(versions_dir: str, volume_name: str, volume_dir: str) -> None:
+    """Perform incremental file backup of a Docker volume."""
+    dest = os.path.join(volume_dir, "files") + "/"
+    pathlib.Path(dest).mkdir(parents=True, exist_ok=True)
+
+    last = get_last_backup_dir(versions_dir, volume_name, dest)
+    link_dest = f"--link-dest='{last}'" if last else ""
+    source = get_storage_path(volume_name)
+
+    cmd = f"rsync -abP --delete --delete-excluded {link_dest} {source} {dest}"
+
+    try:
+        execute_shell_command(cmd)
+    except BackupException as e:
+        if "file has vanished" in str(e):
+            print("Warning: Some files vanished before transfer. Continuing.", flush=True)
+        else:
+            raise