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/api/user/utils.py

@@ -0,0 +1,75 @@
+"""Centralized utilities for API routes.
+
+Post-Mongo-cutover slim: the old Mongo-shaped helpers (``validate_object_id``,
+``check_resource_ownership``, ``paginated_response``, ``serialize_object_id``,
+``safe_db_operation``, ``validate_enum``, ``extract_sort_params``) have been
+removed — they carried ``bson`` / ``pymongo`` imports and had zero callers.
+"""
+
+from functools import wraps
+from typing import Callable, Optional
+
+from flask import (
+    Response,
+    jsonify,
+    make_response,
+    request,
+)
+
+
+def get_user_id() -> Optional[str]:
+    """Extract user ID from decoded JWT token, or None if unauthenticated."""
+    decoded_token = getattr(request, "decoded_token", None)
+    return decoded_token.get("sub") if decoded_token else None
+
+
+def require_auth(func: Callable) -> Callable:
+    """Decorator to require authentication. Returns 401 when absent."""
+
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        user_id = get_user_id()
+        if not user_id:
+            return make_response(jsonify({"success": False, "error": "Unauthorized"}), 401)
+        return func(*args, **kwargs)
+
+    return wrapper
+
+
+def success_response(
+    data=None, message: Optional[str] = None, status: int = 200
+) -> Response:
+    """Shape a successful JSON response."""
+    body = {"success": True}
+    if data is not None:
+        body["data"] = data
+    if message is not None:
+        body["message"] = message
+    return make_response(jsonify(body), status)
+
+
+def error_response(message: str, status: int = 400, **kwargs) -> Response:
+    """Shape an error JSON response; any kwargs are merged into the body."""
+    body = {"success": False, "error": message, **kwargs}
+    return make_response(jsonify(body), status)
+
+
+def require_fields(required: list) -> Callable:
+    """Decorator: return 400 if any listed field is missing/falsy in the JSON body."""
+
+    def decorator(func: Callable) -> Callable:
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            data = request.get_json()
+            if not data:
+                return error_response("Request body required")
+            missing = [field for field in required if not data.get(field)]
+            if missing:
+                return error_response(
+                    f"Missing required fields: {', '.join(missing)}"
+                )
+            return func(*args, **kwargs)
+
+        return wrapper
+
+    return decorator