feat(ads): banner message editor — top help aside + multi-line fields

Admin campaign editor polish:
- move the link-formatting help aside to the top of the Messages section,
  beside the intro note (~40% width), so it no longer drops below and stretches
  the form fields.
- make the English/Russian message fields 3-row, vertically resizable textareas
  (was single-line inputs) so long text wraps instead of scrolling off to the
  right. The strip is white-space:nowrap, so a stray newline collapses to a space
  on display.

backend/internal/adminconsole/assets/console.css

@@ -86,13 +86,13 @@ h1 { font-size: 1.4rem; margin: 0 0 0.4rem; }
   font: inherit;
 }
 .form textarea { min-height: 4rem; resize: vertical; }
-/* A form beside a static help aside (e.g. message-formatting hints). The form keeps its
-   own max-width; the aside fills the remainder and wraps below on a narrow viewport. */
-.form-help { display: flex; flex-wrap: wrap; gap: 1rem; align-items: flex-start; }
+/* A static help aside (e.g. message-formatting hints) beside an intro note at the top of a
+   section: the note fills the row, the aside takes ~40% and both wrap on a narrow viewport. */
+.help-top { display: flex; flex-wrap: wrap; gap: 1rem; align-items: flex-start; margin: 0.2rem 0 0.6rem; }
+.help-top .note { flex: 1 1 16rem; margin: 0; }
 .help {
-  flex: 1 1 16rem;
-  min-width: 14rem;
-  max-width: 30rem;
+  flex: 0 1 40%;
+  min-width: 16rem;
   background: var(--panel-hi);
   border: 1px solid var(--line);
   border-radius: 6px;