refactor(ui/design): card grid, SMTP split, TemplateEdit vertical-stack

Templates: <h4> in flex header, Expand/Collapse moved into a Bulk
actions dropdown, hover-visible kebab on tree nodes with aria-labels.
TreeView CSS gets a .tv-kebab opacity-on-hover utility.

TemplateCreate: form-control (not -sm) for primary inputs; accessible
Back button.

TemplateEdit: Properties card vertical-stacked with Save at the
bottom-right and Parent rendered as readonly plaintext. Add-member
forms (Attributes, Alarms, Scripts, Compositions) reflowed from
horizontal row g-2 align-items-end into cards with stacked col-12
inputs (Scripts gets rows=10). Lock/Unlock badges show full words.
Per-row Delete moved into a kebab dropdown. Tab nav gains
role="tablist" / role="tab" / aria-selected / aria-controls and panels
get role="tabpanel". Validation entries get consistent strong-and-
muted styling.

SharedScripts: migrated from table to card grid (col-lg-6) matching
Sites; cards show code preview + param/return badges + Edit + kebab.
Search filter, empty state CTA, @key.

SharedScriptForm: small ?-icon tooltips next to Parameters and Return
Definition labels.

ExternalSystems: SMTP split out to its own page; remaining tabs (
External Systems, DB Connections, Notification Lists, API Methods,
API Keys) unified as card grids with per-tab search + empty-state CTA.
Tab nav gets full ARIA instrumentation. Header gains a link to the
new SMTP page.

New page SmtpConfiguration.razor at /design/smtp: vertical-stacked
form using the existing Credentials field on the entity.

ExternalSystemForm: AuthConfig placeholder updates based on the
selected AuthType (None / ApiKey / BasicAuth).

DbConnectionForm: form-text below Connection String noting that the
value is stored in plain text and is admin-only.

ApiMethodForm: Script textarea rows=10; JSON example placeholders
for Params and Returns.

NotificationListForm: form-control sizing on Name/email inputs;
thead.table-dark -> table-light on the recipients table.

src/ScadaLink.CentralUI/Components/Shared/TreeView.razor.css

@@ -133,3 +133,20 @@
 [role="treeitem"][aria-expanded="true"] > .tv-row .tv-toggle .bi-chevron-right {
     transform: rotate(90deg);
 }
+
+/* Per-row kebab (More actions): hidden by default, revealed on row hover or when
+   the dropdown is open. Consumers render `<span class="tv-kebab ...">` inside
+   NodeContent to opt in. */
+.tv-row .tv-kebab {
+    flex: 0 0 auto;
+    opacity: 0;
+    transition: opacity 0.1s linear;
+    margin-left: 0.25rem;
+}
+
+.tv-row:hover .tv-kebab,
+.tv-row:focus-within .tv-kebab,
+.tv-row .tv-kebab.show,
+.tv-row .tv-kebab .show {
+    opacity: 1;
+}