fix(kanban): restore Enter=submit, Shift+Enter=newline in inline-create textarea

The textarea conversion in the previous commit dropped Enter-to-submit
entirely, requiring a mouse click on Create for every single-line task.
Restore the common-case shortcut while preserving multiline entry:

- Enter (no modifier) submits the form
- Shift+Enter inserts a newline
- Escape still cancels

Matches the convention used by Slack, Discord, GitHub PR comment boxes.

plugins/kanban/dashboard/dist/index.js

@@ -1760,6 +1760,7 @@
         value: title,
         onChange: function (e) { setTitle(e.target.value); },
         onKeyDown: function (e) {
+          if (e.key === "Enter" && !e.shiftKey) { e.preventDefault(); submit(); }
           if (e.key === "Escape") props.onCancel();
         },
         placeholder: props.columnName === "triage"