Add fallback for empty cards in sections view (#28565)

* Initial plan

* Add edit-mode class to container in hui-grid-section to enable minimum card height

Co-authored-by: piitaya <5878303+piitaya@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: piitaya <5878303+piitaya@users.noreply.github.com>

src/panels/lovelace/sections/hui-grid-section.ts

@@ -99,7 +99,7 @@ export class GridSection extends LitElement implements LovelaceSectionElement {
         @item-removed=${this._cardRemoved}
         invert-swap
       >
-        <div class="container">
+        <div class="container ${classMap({ "edit-mode": editMode })}">
           ${repeat(
             cardsConfig,
             (cardConfig) => this._getKey(cardConfig),