refactor: rename the application package to docsgpt

The backend import package is now docsgpt, the name it will carry on PyPI;
application was far too generic to install into anyone's site-packages.
git mv plus a mechanical rewrite of every import, dotted string and path
reference: 734 Python files, the compose files, Dockerfile, workflows, docs,
setup scripts, devcontainer, k8s manifests, vscode config, pytest and coverage
config, .gitignore. Behaviour is unchanged.

Kept for one release:
- A top-level application package whose meta-path finder resolves
  application.x.y to the already-imported docsgpt.x.y object, so old imports
  and entry points (celery -A application.app.celery,
  uvicorn application.asgi:asgi_app) keep working with a FutureWarning.
- Celery registers every application.* task name as an alias of its
  docsgpt.* task on start-up, so messages queued by the previous release still
  run. The redbeat key prefix moves to redbeat:docsgpt:v2: so schedule entries
  the previous release wrote are left unread instead of firing twice.

The backend image builds from the repository root (docker build -f
docsgpt/Dockerfile .) so it can ship the alias package; a root .dockerignore
allow-lists docsgpt/ and application/ and keeps caches, local data, .env
files, the sample index files and the Dockerfile out. Compose and the image
workflows point at the new context.

docsgpt/agents/tools/path_utils.py

@@ -0,0 +1,34 @@
+from pathlib import Path
+from typing import Optional
+
+
+def validate_tool_path(path: str) -> Optional[str]:
+    """Validate and normalize a tool file path, or return None if invalid.
+
+    Shared by MemoryTool and WikiTool. Strips whitespace, ensures a leading
+    slash, rejects directory traversal (``..`` or ``//``), and preserves a
+    trailing slash to mark directories.
+
+    Args:
+        path: User-provided path.
+
+    Returns:
+        Normalized path, or None if the path is empty or invalid.
+    """
+    if not path:
+        return None
+    path = path.strip()
+    is_directory = path.endswith("/")
+    if not path.startswith("/"):
+        path = "/" + path
+    if ".." in path or path.count("//") > 0:
+        return None
+    try:
+        normalized = str(Path(path).as_posix())
+        if not normalized.startswith("/"):
+            return None
+        if is_directory and not normalized.endswith("/") and normalized != "/":
+            normalized = normalized + "/"
+        return normalized
+    except Exception:
+        return None