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/admin_docs/configuration/country-map-tools.mdx

@@ -0,0 +1,40 @@
+---
+title: Country Map Tools
+sidebar_position: 10
+version: 1
+---
+
+import countriesData from '../../data/countries.json';
+
+# The Country Map Visualization
+
+The Country Map visualization allows you to plot lightweight choropleth maps of
+your countries by province, states, or other subdivision types. It does not rely
+on any third-party map services but would require you to provide the
+[ISO-3166-2](https://en.wikipedia.org/wiki/ISO_3166-2) codes of your country's
+top-level subdivisions. Comparing to a province or state's full names, the ISO
+code is less ambiguous and is unique to all regions in the world.
+
+## Included Maps
+
+The current list of countries can be found in the src
+[legacy-plugin-chart-country-map/src/countries.ts](https://github.com/apache/superset/blob/master/superset-frontend/plugins/legacy-plugin-chart-country-map/src/countries.ts)
+
+The Country Maps visualization already ships with the maps for the following countries:
+
+<ul style={{columns: 3}}>
+{countriesData.countries.map((country, index) => (
+  <li key={index}>{country}</li>
+))}
+</ul>
+
+## Adding a New Country
+
+To add a new country to the list, you'd have to edit files in
+[@superset-ui/legacy-plugin-chart-country-map](https://github.com/apache/superset/tree/master/superset-frontend/plugins/legacy-plugin-chart-country-map).
+
+1. Generate a new GeoJSON file for your country following the guide in [this Jupyter notebook](https://github.com/apache/superset/blob/master/superset-frontend/plugins/legacy-plugin-chart-country-map/scripts/Country%20Map%20GeoJSON%20Generator.ipynb).
+2. Edit the countries list in [legacy-plugin-chart-country-map/src/countries.ts](https://github.com/apache/superset/blob/master/superset-frontend/plugins/legacy-plugin-chart-country-map/src/countries.ts).
+3. Install superset-frontend dependencies: `cd superset-frontend && npm install`
+4. Verify your countries in Superset plugins storybook: `npm run plugins:storybook`.
+5. Build and install Superset from source code.