docs: bifurcate documentation into user, admin, and developer sections

Major restructuring of documentation to separate concerns:

**New Structure:**
- `/docs/` - User-facing docs (intro, quickstart, databases, using-superset, faq)
- `/admin-docs/` - Administrator docs (installation, configuration, security)
- `/developer-docs/` - Developer docs (contributing, extensions, guidelines, testing)

**Changes:**
- Move installation, configuration, and security docs to admin_docs/
- Move contributing, extensions, guidelines, and testing to developer_docs/
- Rename developer_portal to developer_docs (with underscore to hyphen in URL)
- Add sidebarAdminDocs.js for admin documentation navigation
- Update versions-config.json with new doc sections
- Update docusaurus.config.ts with new plugins and redirects
- Update internal links in versioned docs (6.0.0) to use new paths
- Keep user-facing content (databases, using-superset, faq) in main docs

This separation makes it clearer which documentation is relevant for:
- End users exploring and visualizing data
- Administrators deploying and configuring Superset
- Developers contributing to or extending Superset

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/developer_docs/extensions/deployment.md

@@ -0,0 +1,49 @@
+---
+title: Deployment
+sidebar_position: 7
+---
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Deployment
+
+Once an extension has been developed, the deployment process involves packaging and uploading it to the host application.
+
+Packaging is handled by the `superset-extensions bundle` command, which:
+
+1. Builds frontend assets using Webpack (with Module Federation configuration).
+2. Collects backend Python source files and all necessary resources.
+3. Generates a `manifest.json` with build-time metadata, including the contents of `extension.json` and references to built assets.
+4. Packages everything into a `.supx` file (a zip archive with a specific structure required by Superset).
+
+To deploy an extension, place the `.supx` file in the extensions directory configured via `EXTENSIONS_PATH` in your `superset_config.py`:
+
+``` python
+EXTENSIONS_PATH = "/path/to/extensions"
+```
+
+During application startup, Superset automatically discovers and loads all `.supx` files from this directory:
+
+1. Scans the configured directory for `.supx` files.
+2. Validates each file is a properly formatted zip archive.
+3. Extracts and validates the extension manifest and metadata.
+4. Loads the extension, making it available for use.
+
+This file-based approach simplifies deployment in containerized environments and enables version control of extensions alongside infrastructure configuration.