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/lib/Controller/PageController.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\Astroglobe\Controller;
+
+use OCA\Astroglobe\AppInfo\Application;
+use OCP\AppFramework\Controller;
+use OCP\AppFramework\Http\Attribute\FrontpageRoute;
+use OCP\AppFramework\Http\Attribute\NoAdminRequired;
+use OCP\AppFramework\Http\Attribute\NoCSRFRequired;
+use OCP\AppFramework\Http\Attribute\OpenAPI;
+use OCP\AppFramework\Http\TemplateResponse;
+
+/**
+ * @psalm-suppress UnusedClass
+ */
+class PageController extends Controller {
+	#[NoCSRFRequired]
+	#[NoAdminRequired]
+	#[OpenAPI(OpenAPI::SCOPE_IGNORE)]
+	#[FrontpageRoute(verb: 'GET', url: '/')]
+	public function index(): TemplateResponse {
+		return new TemplateResponse(
+			Application::APP_ID,
+			'index',
+		);
+	}
+}