feat(astrolabe): add Nextcloud PHP app for MCP server management

Adds a native Nextcloud app "Astroglobe" that provides:
- Personal settings: OAuth authorization for background MCP access
- Admin settings: Server status and vector sync monitoring
- API endpoints for MCP server communication

The app uses PKCE OAuth flow to obtain tokens for the MCP server,
enabling features like background vector sync per ADR-018.

Includes:
- PHP app structure (controllers, services, settings)
- Vue.js frontend components
- Docker compose mount configuration
- Installation hook for development testing
- ADR-018 documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

third_party/astroglobe/CODE_OF_CONDUCT.md

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+In the Nextcloud community, participants from all over the world come together to create Free Software for a free internet. This is made possible by the support, hard work and enthusiasm of thousands of people, including those who create and use Nextcloud software.
+
+Our code of conduct offers some guidance to ensure Nextcloud participants can cooperate effectively in a positive and inspiring atmosphere, and to explain how together we can strengthen and support each other.
+
+The Code of Conduct is shared by all contributors and users who engage with the Nextcloud team and its community services. It presents a summary of the shared values and “common sense” thinking in our community.
+
+You can find our full code of conduct on our website: https://nextcloud.com/code-of-conduct/
+
+Please, keep our CoC in mind when you contribute! That way, everyone can be a part of our community in a productive, positive, creative and fun way.