Let admins create and delete users in Benutzerverwaltung, modernize list

Wire up two previously-unwired stored procedures for the usr module:
- fis_admin_createUserAccount gained the missing @authaccount +
  intranet_admin auth gate, a duplicate-email check, and now returns
  the (possibly auto-generated) password so it can be emailed to the
  new user, mirroring fis_admin_resetUserPassword's pattern.
- fis_admin_delUserAccount gained the same missing auth gate plus a
  guard against an admin deleting their own account.

New /do/usr/create and /do/usr/delete endpoints in
IntranetController.AdminUsers.cs, a "Neuer Benutzer" button and a
"Benutzer löschen" ribbon action in fis.usr.js, and unit tests for the
new welcome-email content (BuildWelcomeEmail).

Also restyle the user list (fis.usr.scss) from a plain bordered table
to a card-style row grid with avatar-initial badges and status pills,
matching the Admin dashboard's visual language.

Documented as ADR 0020 and in the admin-user-management concept doc.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Fuchs/wwwroot/web/fis.usr.css

@@ -16,29 +16,87 @@
 /* #1b4379  #0033b3 */
 /*neu: #56a532  ; alt: rgb(32,144,119);*/
 /* 10% sw */
-.usrfrm > table {
-  border-collapse: collapse;
-  margin: 2rem;
+.usrfrm {
+  padding: 1.5rem 2rem;
 }
-.usrfrm > table th {
-  padding: 0.2rem 0.35rem;
-  border: 1px solid #CCC;
+.usrfrm .usr_grid {
+  border: 1px solid #e2e2e2;
+  border-radius: 0.5rem;
+  background: #fff;
+  box-shadow: 0 1px 3px rgba(50, 50, 50, 0.1);
+  overflow: hidden;
 }
-.usrfrm > table td {
-  padding: 0.2rem 0.35rem;
-  border: 1px solid #CCC;
+.usrfrm .usr_row {
+  display: grid;
+  grid-template-columns: 2.75rem 1.6fr 1.8fr 8rem;
+  align-items: center;
+  gap: 0.75rem;
+  padding: 0.55rem 1rem;
+  border-bottom: 1px solid #eee;
 }
-.usrfrm > table tr {
+.usrfrm .usr_row:last-child {
+  border-bottom: none;
+}
+.usrfrm .usr_row_hd {
+  background: rgb(27, 67, 121);
+  color: #fff;
+  font-weight: bold;
+  font-size: 0.85rem;
+  text-transform: uppercase;
+  letter-spacing: 0.02em;
+  padding: 0.5rem 1rem;
+}
+.usrfrm .usr_row:not(.usr_row_hd) {
   cursor: pointer;
+  transition: background-color 0.12s ease-in-out;
 }
-.usrfrm > table tr:nth-child(2n+1) td {
-  background-color: #EEE;
-}
-.usrfrm > table tr:hover td {
+.usrfrm .usr_row:not(.usr_row_hd):hover {
   background-color: #f3f6fb;
 }
-.usrfrm > table tr.selected td {
-  background-color: lightblue;
+.usrfrm .usr_row:not(.usr_row_hd).selected {
+  background-color: rgba(86, 165, 50, 0.12);
+  box-shadow: inset 3px 0 0 rgb(86, 165, 50);
+}
+.usrfrm .usr_avatar {
+  width: 2.1rem;
+  height: 2.1rem;
+  border-radius: 50%;
+  background: rgb(27, 67, 121);
+  color: #fff;
+  font-size: 0.78rem;
+  font-weight: bold;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+.usrfrm .usr_col_name {
+  font-weight: 600;
+  color: #222;
+}
+.usrfrm .usr_col_email {
+  color: #555;
+  overflow-wrap: anywhere;
+}
+.usrfrm .usr_pill {
+  display: inline-block;
+  padding: 0.1rem 0.6rem;
+  border-radius: 1rem;
+  font-size: 0.78rem;
+  font-weight: bold;
+  white-space: nowrap;
+}
+.usrfrm .usr_pill_on {
+  background: #e2f3da;
+  color: #2f6d18;
+}
+.usrfrm .usr_pill_off {
+  background: #ececec;
+  color: #777;
+}
+.usrfrm .usr_empty {
+  padding: 1.5rem 1rem;
+  text-align: center;
+  color: #777;
 }
 .usrfrm .usr_err {
   padding: 1rem 2rem;
@@ -46,6 +104,31 @@
   font-weight: bold;
 }
 
+@media (max-width: 640px) {
+  .usrfrm {
+    padding: 0.75rem;
+  }
+  .usrfrm .usr_row {
+    grid-template-columns: 2.25rem 1fr;
+    grid-template-areas: "avatar name" "avatar email" "avatar status";
+  }
+  .usrfrm .usr_row_hd {
+    display: none;
+  }
+  .usrfrm .usr_avatar {
+    grid-area: avatar;
+  }
+  .usrfrm .usr_col_name {
+    grid-area: name;
+  }
+  .usrfrm .usr_col_email {
+    grid-area: email;
+    font-size: 0.85rem;
+  }
+  .usrfrm .usr_col_status {
+    grid-area: status;
+  }
+}
 .usr_groups_dlg {
   padding: 0.25rem 0;
 }