Add Administration, starting with accounts

An account whose Stalwart role manages accounts now finds Administration in
the account menu. It lists, searches, creates and edits accounts -- display
name, other addresses, role, storage limit -- sets a new password, and
deletes, each offered only when the role holds the matching permission.

The server keeps the permissions list from GET /api/account, which it
already called for the edition and threw the rest away. Everything else is
JMAP x:Account, x:Domain and x:Role calls through the existing /api/jmap
proxy, so nothing new is stored and Stalwart decides every call.

Stalwart checks a grant against the caller's permissions but not a password
change or a delete, so an account that outranks the viewer is shown
read-only. Your own password is changed in Settings, which re-seals the
session; changing it here would strand it.

The mock server gains a directory behind the same permission names, with
MOCK_ROLE choosing admin, tenant-admin, helpdesk or user.

68 new strings, translated in all nine catalogues; strings falling back to
English stay at 16.

web/src/views/admin/AdminView.tsx

@@ -0,0 +1,41 @@
+import { Link, Redirect, useLocation } from "wouter";
+import { ArrowLeft, User } from "lucide-react";
+import { hasAdministration } from "@/lib/adminAccess";
+import { t } from "@/lib/i18n";
+import { AccountsAdmin } from "./AccountsAdmin";
+import { usePermissions } from "./usePermissions";
+
+/**
+ * Administration: what the signed-in account's Stalwart role lets it manage.
+ *
+ * Laid out like Settings, because it is the same kind of place -- a list of
+ * sections and the one that is open -- and on a phone it behaves the same way,
+ * the list first and a section on its own. Accounts is the only section so
+ * far; the nav is written as a list so the next one is an entry, not a rework.
+ */
+export function AdminView({ section, id }: { section?: string; id?: string }) {
+  const [, navigate] = useLocation();
+  const perms = usePermissions();
+  // Typed in by hand, or a role taken away since the menu was drawn. Stalwart
+  // would refuse every call anyway; this spares the page of refusals.
+  if (!hasAdministration(perms)) return <Redirect to="/mail" />;
+  return (
+    <div className={`settings-layout admin-layout ${section ? "section" : "root"}`}>
+      <nav className="settings-nav" aria-label={t("Administration")}>
+        <div className="nav-section" style={{ paddingLeft: 8 }}><span>{t("Directory")}</span></div>
+        <Link href="/admin/accounts" className={`nav-item ${!section || section === "accounts" ? "active" : ""}`}>
+          <User size={18} />
+          <span className="nav-label">{t("Accounts")}</span>
+        </Link>
+      </nav>
+      <div className="settings-content admin-content">
+        {section && (
+          <button className="btn btn-ghost btn-sm admin-back" style={{ marginBottom: 8, marginLeft: -8 }} onClick={() => navigate("/admin")}>
+            <ArrowLeft size={16} /> {t("Administration")}
+          </button>
+        )}
+        <AccountsAdmin selectedId={id} />
+      </div>
+    </div>
+  );
+}