Added: A naming standard page states sevenx as 7x's public PHP code prefix and exp as the Exponential project prefix

sevenx is the official public PHP code prefix of 7x, because a class or
identifier cannot start with a digit. Extensions and classes from 7x use
sevenx or exp as needed; exp is used with intent to build the Exponential
brand and to assign ownership to the Exponential project and the
Exponential Foundation.

The coding standards, layering and naming rules, extension book chapters,
glossaries, CONTRIBUTING.md, the extension skeleton cookbook and the brand
pages for partners, advocates and the press now state the rule and link
the new page. The brand rules no longer say that no written rule exists,
and the app creators' page no longer tells third parties to use exp.

Merge remote-tracking branch 'origin/main' into worktree-agent-af5aa7e5fe22fdfe0

# Conflicts:
#	doc/de/.dirnames.json
#	doc/de/.paths.json
#	share/filelist.md5

Added: German translation of help/template-language (29 pages)

Added: German translation of help/site-packages (78 pages)

Translates the site packages section into German: the basics of site installer packages, the package server, the documentation requirements, sevenx_multisite and cjw_multisite, making and publishing a site package of one's own, and the package pages of the administration.

Updated: The help sidebar has a Browse all help button and a Help Start button

The viewer's sidebar linked to the contents page with a small plain link
that was easy to miss. It is now a button with the list icon, and a second
button beside it, Help Start, goes back to the help dashboard, so a reader
deep in a long page or a long tree has both one click away.

- design/admin and design/admin4 viewer.tpl: the two buttons (a4-btn
  a4-btn-small, with icons) in a new a4-help-nav-go row under the filter.
- modules/help.css (both designs): the two buttons share their row in equal
  halves and a label wraps inside its button in the narrow sidebar; in the
  wide layout only the page tree scrolls inside the sticky sidebar, so the
  filter and the buttons stay in the window. The unused a4-help-nav-all rule
  is gone.
- "Help Start" (kernel/exphelp) in the untranslated catalogue and a
  translation in each of the 23 complete catalogues.

Updated: The security policy follows the release history in the help's page tree

PageOrder[project/SECURITY.md] is 50 (was 150), in exphelp.ini and the built-in default, so the
page tree lists it right after the release history.

Added: German translation of help/hosting (140 pages)

Translates the hosting section for system administrators and product managers at hosting companies into German: basics, business, checklists, migrations, hosting models, operations, control panels, performance, provisioning, runbooks, security and web servers. Pages of the customer and partner sections that link into the hosting section now point to the German pages.