fix(dashboard): widgets hold their place as content loads and the window resizes (#5713)

Wider than 12 columns, pack() took the first free spot for each widget's
content-fitted height, and that height changes as each widget's content
arrives and on every poll, so widgets traded columns and order as the page
loaded (CI 9107: test_dash_layout fails at 16, 18 and 24 columns on the old
pack()). Now columns and order are decided at the saved heights, from the
saved layout and the column count alone; each widget then drops at its
fitted height onto what is above it in its columns, so content only closes
gaps.

The dashboard moves widgets into place in two passes, below everything first
and then up, so Gridstack never pushes a not-yet-moved widget out of its
place on the way. The share view passes saved heights the same way.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/templates/dashboard/share_view.html

@@ -76,7 +76,7 @@ document.addEventListener('DOMContentLoaded', function () {
   function relayout() {
     var cols = L.columnsFor(grid.clientWidth);
     var pos = L.pack(cells().map(function (el) {
-      var s = L.viewed(el); s.id = el.dataset.id; s.h = el._fitH || s.h; return s;
+      var s = L.viewed(el); s.id = el.dataset.id; s.full = s.h; s.h = el._fitH || s.h; return s;
     }), cols);
     grid.style.gridTemplateColumns = 'repeat(' + cols + ', 1fr)';
     cells().forEach(function (el) {