[v2] feat: add version api endpoint

[svenvg93]

📃 Description

This PR adds an API endpoint to check the app version and if there is an update available.

{
    "data": {
        "app": {
            "version": "v1.13.7",
            "build_date": "2026-02-04T00:00:00+00:00"
        },
        "updates": {
            "latest_version": "v1.13.9",
            "update_available": true
        }
    },
    "message": "ok"
}

Closes #2701

📖 Documentation

OpenAPI spec is updated.

🪵 Changelog

➕ Added

• admin:read token for this API endpoint.
• VersionController exposes the current and latest version and performs an update availability check.
• /version route in /api/v1