Refactor Nextcloud configuration to use OCC script approach and add email/OIDC support

Major architectural changes:
- Replace config file templating with unified OCC command script
- Remove custom_apps mount overlay that caused Caddy serving issues
- Implement script-based configuration for idempotency and clarity

Configuration improvements:
- Add email/SMTP support with master switch (nextcloud_email_enabled)
- Add OIDC/SSO integration with Authentik support
- Add apps installation (user_oidc, calendar, contacts)
- Enable group provisioning and quota management from OIDC
- Set nextcloud_oidc_unique_uid to false per Authentik docs

Files removed:
- nextcloud.config.php.j2 (replaced by OCC commands)
- redis.config.php.j2 (replaced by OCC commands)
- optimization.yml (merged into configure.yml)

Files added:
- configure-nextcloud.sh.j2 (single source of truth for config)
- configure.yml (deploys and runs configuration script)

Documentation:
- Add comprehensive OIDC setup guide with Authentik integration
- Document custom scope mapping and group provisioning
- Add email configuration examples for common providers
- Update vault variables documentation
- Explain two-phase deployment approach

Host configuration:
- Change admin user from 'admin' to 'joakim'
- Add admin email configuration

roles/nextcloud/templates/nextcloud.container

@@ -23,9 +23,6 @@ Volume={{ nextcloud_data_dir }}:/var/www/html/data:Z
 # Configuration (private - contains secrets)
 Volume={{ nextcloud_config_dir }}:/var/www/html/config:Z
 
-# Custom apps (world-readable)
-Volume={{ nextcloud_custom_apps_dir }}:/var/www/html/custom_apps:Z
-
 # Infrastructure sockets (mounted with world-readable permissions on host)
 Volume={{ postgresql_unix_socket_directories }}:{{ postgresql_unix_socket_directories }}:Z
 Volume={{ valkey_unix_socket_path | dirname }}:{{ valkey_unix_socket_path | dirname }}:Z