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.

tests/integration/test_scim.py

@@ -19,10 +19,10 @@ from unittest.mock import patch
 import pytest
 from sqlalchemy import text
 
-from application.core.settings import settings
-from application.storage.db.repositories.auth_events import AuthEventsRepository
-from application.storage.db.repositories.users import UsersRepository
-from application.storage.db.session import db_readonly, db_session
+from docsgpt.core.settings import settings
+from docsgpt.storage.db.repositories.auth_events import AuthEventsRepository
+from docsgpt.storage.db.repositories.users import UsersRepository
+from docsgpt.storage.db.session import db_readonly, db_session
 
 SCIM_TOKEN = "scim-test-token"
 AUTH = {"Authorization": f"Bearer {SCIM_TOKEN}"}
@@ -42,7 +42,7 @@ pytestmark = [
 @pytest.fixture(scope="module")
 def app():
     """Real Flask app; /scim/ paths bypass JWT auth so no handle_auth patching is needed."""
-    from application.app import app as flask_app
+    from docsgpt.app import app as flask_app
 
     flask_app.config["TESTING"] = True
     return flask_app
@@ -58,7 +58,7 @@ def scim_env(monkeypatch):
     """Enable SCIM on the settings singleton and stub the Redis denylist."""
     monkeypatch.setattr(settings, "SCIM_ENABLED", True)
     monkeypatch.setattr(settings, "SCIM_TOKEN", SCIM_TOKEN)
-    with patch("application.api.scim.routes.deny_user") as deny_user_mock:
+    with patch("docsgpt.api.scim.routes.deny_user") as deny_user_mock:
         yield SimpleNamespace(deny_user=deny_user_mock)