Add SQLite as a first-class database backend #141

Part of #140 and LibreSign/libresign#8969.

Context

nextcloud-docker-development currently supports MySQL and PostgreSQL as explicit database services, while LibreSign's Behat compatibility matrix also includes SQLite.

The PHP development images currently install MySQL/PostgreSQL PDO extensions but do not install SQLite/PDO_SQLite.

The parent worker contract defines database selection as:

DB_TYPE=sqlite|mysql|mariadb|pgsql

This issue implements the sqlite branch of that contract.

Goal

Add SQLite as a first-class selectable database backend in nextcloud-docker-development.

Requirements

• Install the PHP extensions required by Nextcloud for SQLite in every supported PHP development image used by the worker lifecycle.
• DB_TYPE=sqlite must select SQLite without requiring a separate database container.
• Install Nextcloud with --database=sqlite when SQLite is selected.
• Keep the SQLite database inside the worker's isolated Nextcloud filesystem.
• Do not use DB_HOST to encode SQLite selection; DB_TYPE owns backend selection.
• Start no MySQL, MariaDB or PostgreSQL database service for a SQLite worker.
• Preserve existing MySQL/PostgreSQL behavior.
• Do not add LibreSign-specific behavior.

Compose/lifecycle behavior

The caller must be able to start a SQLite worker without editing Compose YAML or shell scripts.

The worker lifecycle must not wait for a network database when DB_TYPE=sqlite.

If the current Compose database service abstraction cannot represent “no service”, refactor the lifecycle/Compose layout explicitly rather than starting an unused database container.

Tests

Add automated coverage proving:

• the PHP image exposes SQLite/PDO_SQLite;
• a clean DB_TYPE=sqlite worker installs Nextcloud successfully;
• occ status reports an installed instance;
• data/configuration written in one SQLite worker is not visible in another checkout/worker;
• selecting SQLite does not start or wait for MySQL/MariaDB/PostgreSQL;
• existing MySQL/PostgreSQL setup tests continue to pass.

Documentation

Document a non-interactive example using DB_TYPE=sqlite and explain that no database service/container is required.

Done when

• DB_TYPE=sqlite is supported.
• Required PHP SQLite extensions are present in supported worker images.
• Nextcloud autoinstall works with SQLite.
• SQLite selection does not start or wait for a network database.
• SQLite workers remain isolated per checkout/worker.
• Existing MySQL/PostgreSQL behavior is not regressed.
• Automated tests and documentation cover the new backend.