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/routes.py

@@ -0,0 +1,87 @@
+"""
+Main user API routes - registers all namespace modules.
+"""
+
+from flask import Blueprint
+
+from docsgpt.api import api
+from .agents import (
+    agents_folders_ns,
+    agents_guardrails_ns,
+    agents_ns,
+    agents_portability_ns,
+    agents_sharing_ns,
+    agents_webhooks_ns,
+)
+from .analytics import analytics_ns
+from .artifacts import artifacts_ns
+from .attachments import attachments_ns
+from .conversations import conversations_ns
+from .me import me_ns
+from .models import models_ns
+from .prompts import prompts_ns
+from .schedules import schedules_ns
+from .sharing import sharing_ns
+from .sources import (
+    sources_chunks_ns,
+    sources_ns,
+    sources_search_ns,
+    sources_upload_ns,
+)
+from .teams import teams_ns
+from .tools import tools_mcp_ns, tools_ns
+from .workflows import workflows_ns
+
+
+user = Blueprint("user", __name__)
+
+# Analytics
+api.add_namespace(analytics_ns)
+
+# Artifacts
+api.add_namespace(artifacts_ns)
+
+# Attachments
+api.add_namespace(attachments_ns)
+
+# Conversations
+api.add_namespace(conversations_ns)
+
+# Current user (identity + roles)
+api.add_namespace(me_ns)
+
+# Models
+api.add_namespace(models_ns)
+
+# Agents (main, sharing, webhooks, folders, import/export)
+api.add_namespace(agents_ns)
+api.add_namespace(agents_sharing_ns)
+api.add_namespace(agents_webhooks_ns)
+api.add_namespace(agents_folders_ns)
+api.add_namespace(agents_portability_ns)
+api.add_namespace(agents_guardrails_ns)
+
+# Prompts
+api.add_namespace(prompts_ns)
+
+# Schedules
+api.add_namespace(schedules_ns)
+
+# Sharing
+api.add_namespace(sharing_ns)
+
+# Sources (main, chunks, retrieval test, upload)
+api.add_namespace(sources_ns)
+api.add_namespace(sources_chunks_ns)
+api.add_namespace(sources_search_ns)
+api.add_namespace(sources_upload_ns)
+
+# Teams (CRUD, membership, resource-sharing grants)
+api.add_namespace(teams_ns)
+
+# Tools (main, MCP)
+api.add_namespace(tools_ns)
+api.add_namespace(tools_mcp_ns)
+
+# Workflows
+api.add_namespace(workflows_ns)