feat: add pagination support for project lists in dialogs

Add server-side pagination to EntityGrid component for projects, enabling
infinite scrolling to load all available projects instead of stopping after
the initial batch.

Changes:
- EntityGrid: Add loadMoreCallback prop to trigger server-side loading when
  scroll reaches end of loaded projects
- OnboardMeetingSetupView: Update loadProjects() to support pagination with
  beforeId parameter and add handleLoadMoreProjects() callback
- MeetingProjectDialog: Accept and pass through loadMoreCallback to EntityGrid
- GiftedDialog: Add pagination support to loadProjects() and
  handleLoadMoreProjects() callback
- EntitySelectionStep: Accept and pass through loadMoreCallback prop to
  EntityGrid when showing projects

This ensures users can access all projects in MeetingProjectDialog and
GiftedDialog by automatically loading more as they scroll, matching the
behavior already present in DiscoverView.

All project uses of EntityGrid now use pagination by default.

src/components/MeetingProjectDialog.vue

@@ -16,6 +16,7 @@
         :show-unnamed-entity="false"
         :notify="notify"
         :conflict-context="'project'"
+        :load-more-callback="loadMoreCallback"
         @entity-selected="handleEntitySelected"
       />
 
@@ -77,6 +78,10 @@ export default class MeetingProjectDialog extends Vue {
   @Prop()
   notify?: (notification: NotificationIface, timeout?: number) => void;
 
+  /** Callback function to load more projects from server */
+  @Prop()
+  loadMoreCallback?: (entities: PlanData[]) => Promise<void>;
+
   /**
    * Handle entity selection from EntityGrid
    * Immediately assigns the selected project and closes the dialog