feat: add Nextcloud Collectives app support (#621)

Implement MCP tools for the Collectives wiki/documentation app, enabling
agentic workflows for team knowledge base management.

16 tools covering collectives, pages, tags, search, and trash:
- Read: list collectives, list/get pages (with WebDAV content), search,
  list tags, list trashed pages
- Write: create/update collective, create/move/trash/restore pages,
  set emoji, create/assign/remove tags

Includes Docker hook for app installation, OCS API client with envelope
unwrapping, Pydantic models, unit tests (16), and integration tests (10).

Closes #621

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app-hooks/post-installation/10-install-collectives-app.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+set -euox pipefail
+
+echo "Installing and configuring collectives app for testing..."
+
+# Collectives depends on Circles (teams) - ensure it's enabled
+# Circles is bundled with Nextcloud, so just enable it
+php /var/www/html/occ app:enable circles
+
+# Check if development collectives app is mounted at /opt/apps/collectives
+if [ -d /opt/apps/collectives ]; then
+    echo "Development collectives app found at /opt/apps/collectives"
+
+    # Remove any existing collectives app in apps (from app store or old symlink)
+    if [ -e /var/www/html/custom_apps/collectives ]; then
+        echo "Removing existing collectives in apps..."
+        rm -rf /var/www/html/custom_apps/collectives
+    fi
+
+    # Create symlink from apps to the mounted development version
+    # Per Nextcloud docs: apps outside server root need symlinks in server root
+    echo "Creating symlink: custom_apps/collectives -> /opt/apps/collectives"
+    ln -sf /opt/apps/collectives /var/www/html/custom_apps/collectives
+
+    echo "Enabling collectives app from /opt/apps (development mode via symlink)"
+    php /var/www/html/occ app:enable collectives
+elif [ -d /var/www/html/custom_apps/collectives ]; then
+    echo "collectives app directory found in apps (already installed)"
+    php /var/www/html/occ app:enable collectives
+else
+    echo "collectives app not found, installing from app store..."
+    php /var/www/html/occ app:install collectives
+    php /var/www/html/occ app:enable collectives
+fi