Add Mailing lists to Administration

A mailing list is an address that passes mail on to everyone on it. To
Stalwart it is its own object, x:MailingList, behind sysMailingList*, so
it gets its own section under Directory after Groups: search, fifty to a
page with each list's recipient count, and a panel to create, edit and
delete one.

Recipients are a property of the list, so unlike a group's members they
save with the rest of the panel. What Save sends for them is only what was
added and removed, one recipients/<address> pointer each -- the patch the
live server accepted -- so a recipient added elsewhere while the panel was
open is not taken out. They can be pasted several at a time, from a
spreadsheet column, a comma-separated line or Name <address>; anything with
an @ that is not an address stays in the box with a note. Past a dozen, a
filter narrows them.

That is all a list is in Stalwart -- no owners, moderation or posting
rules -- so that is all the panel offers.

The mock answers x:MailingList with two lists, the recipient set's live
shape, and the refusals a wrong address, a clash with an account and a
missing permission get.

Twenty-five new strings and one plural, in all nine catalogues.

README.md

@@ -83,7 +83,7 @@ More, including the mobile layout, on [ihasmail.org](https://ihasmail.org/#scree
 - **Nine new interface languages** — German, Spanish, French, Dutch, Portuguese (Brazil), Russian, Ukrainian, Simplified Chinese and Japanese, alongside English and separate from the date-and-time locale. Every one is marked **Beta**: they were made by AI and no native speaker has read them yet, which Settings says plainly, with a link for reporting anything wrong
 - **Twelve themes** — Classic and ihasmail's own, plus Catppuccin, Dracula, Gruvbox, Rosé Pine, Tokyo Night, Solarized, Ayu, Kanagawa, Everforest and Primer, each with the light and dark half its own project publishes. Palette and light-or-dark are separate choices, and the accent colour still sits on top of any of them. Only published colour values are used, taken from each project's own repository; the shades between them are derived and every text colour is measured against the surface it sits on, so a palette that would not meet the contrast this app claims is not written at all — see [Themes](FEATURES.md#themes)
 - **On a phone** — swipe a message to archive or delete it (either direction, your choice), hold one to select it, hold a folder for its menu, pull the list to refresh, swipe back from a conversation
-- **Administration** — for an account whose Stalwart role manages accounts or domains, from the account menu: a dashboard of users, domains, queued mail, memory and the last day's received and sent, scoped to a tenant administrator's own tenancy; create, edit and delete accounts and set their passwords; create groups and add or remove their members; add domains, copy their DNS records one at a time or as a zone file, see their DKIM keys, and remove them once nothing uses them. Each control is there only when the role allows it, and Stalwart decides every call. Only for a session signed in with *This is my own device* ticked, and `ADMINISTRATION=0` turns it off for everyone — see [Administration](FEATURES.md#administration)
+- **Administration** — for an account whose Stalwart role manages accounts or domains, from the account menu: a dashboard of users, domains, queued mail, memory and the last day's received and sent, scoped to a tenant administrator's own tenancy; create, edit and delete accounts and set their passwords; create groups and add or remove their members; create mailing lists and paste in their recipients; add domains, copy their DNS records one at a time or as a zone file, see their DKIM keys, and remove them once nothing uses them. Each control is there only when the role allows it, and Stalwart decides every call. Only for a session signed in with *This is my own device* ticked, and `ADMINISTRATION=0` turns it off for everyone — see [Administration](FEATURES.md#administration)
 - **Platform** — installable PWA, Web Push with ihasmail closed, `mailto:` handler, no credentials in the browser, strict CSP, SSRF-safe image proxy
 
 The long version is on [ihasmail.org](https://ihasmail.org/#features); how to