fix(commands): replace undefined :ref:occ with external link

The `occ` label is defined in the admin manual which is a separate
Sphinx build, causing an undefined label warning. Replace with an
absolute URL per the cross-manual linking convention.

Also fix the style guide which incorrectly documented `/latest/`
instead of `/server/latest/` as the cross-manual URL pattern.

Signed-off-by: John Molakvoæ (skjnldsv) <skjnldsv@protonmail.com>
Signed-off-by: skjnldsv <skjnldsv@protonmail.com>

Author: skjnldsv

developer_manual/app_development/commands.rst

@@ -4,7 +4,7 @@
 occ commands
 ============
 
-Nextcloud apps can register custom :ref:`occ <occ>` commands that administrators can run from the command line. Commands extend ``OC\Core\Command\Base``, which wraps
+Nextcloud apps can register custom `occ <https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/occ_command.html>`_ commands that administrators can run from the command line. Commands extend ``OC\Core\Command\Base``, which wraps
 `Symfony Console <https://symfony.com/doc/current/console.html>`_ and adds bash completion support, so the full Symfony
 Console API is available.
 

style_guide.rst

@@ -291,13 +291,12 @@ page moves.
      See :doc:`../configuration_server/config_sample_php_parameters` for all
      available options.
 
-**Different manual — use a** ``docs.nextcloud.com/latest/`` **URL**
+**Different manual — use a** ``docs.nextcloud.com/server/latest/`` **URL**
    When linking from one manual to a page in a different manual (e.g. from the
    User Manual to the Administration Manual), use an absolute URL with
-   ``/latest/`` as the version segment. The build system automatically replaces
-   ``/latest/`` with the correct version number for stable branches::
+   ``/server/latest/`` as the version segment::
 
-     See `Backup configuration <https://docs.nextcloud.com/latest/admin_manual/maintenance/backup.html>`_
+     See `Backup configuration <https://docs.nextcloud.com/server/latest/admin_manual/maintenance/backup.html>`_
      for details.
 
 ``:doc:``