Add OCC commands for global calendar feature opt-in and opt-out in Deck

[Fledermaus-20]

Summary

This pull request introduces new occ commands that allow administrators to globally enable or disable the calendar integration in the Deck app.

These commands provide system-wide control over whether the calendar feature is enabled by default (opt-out mode) or disabled by default (opt-in mode).

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New Commands

# Opt-In Mode (default: disabled unless enabled)
php occ deck:calendar-optin --on     # Enables calendar feature for all users (opt-in mode)
php occ deck:calendar-optin --off    # Disables calendar feature for all users (default)

# Opt-Out Mode (default: enabled unless disabled)
php occ deck:calendar-optout --on    # Enables calendar feature for all users (opt-out mode)
php occ deck:calendar-optout --off   # Disables calendar feature for all users (opt-out mode off)

[luka-nextcloud]

• Why do those commands have exactly the same execution logic?
• The description should be updated a bit since it only works for existing users.

[luka-nextcloud]

@Fledermaus-20 Thanks for your updates. Could you please rebase main and then squash your commits? Thank you for your support.

[luka-nextcloud]

@Fledermaus-20 One more thing, the copyright header is missing for the new added file lib/Command/CalendarToggle.php

[luka-nextcloud]

Could you also run composer run cs:fix to fix the phpcs issue?

[github-actions]

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