fix(web): add load-more pagination for Done column on issue board (#492)

* fix(web): add load-more pagination for Done column on issue board

The Done column was capped at 50 issues with no way to load more.
Track doneTotal in the TQ cache and add a useLoadMoreDoneIssues hook
that fetches the next page and merges it into the unified issue cache.
The Done column now shows a "Load more" button when there are
additional items.

- shared/types/api.ts: add doneTotal to ListIssuesResponse
- core/issues/queries.ts: store doneTotal from the done-status response
- core/issues/mutations.ts: add useLoadMoreDoneIssues hook, update
  create/delete mutations to maintain doneTotal
- core/issues/ws-updaters.ts: maintain doneTotal on WS events
- features/issues/components/board-column.tsx: accept optional footer
- features/issues/components/board-view.tsx: render Load more button
  in Done column

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(web): address review issues in done-column load-more

1. Fix total over-counting: loadMore no longer inflates total since
   the initial query already includes all done issues in total count.
2. Fix onIssueUpdated: maintain doneTotal when issue status changes
   to/from done via WS events.
3. Make doneTotal optional in ListIssuesResponse since it's a
   frontend-only field not returned by the backend API. All reads
   now use ?? 0 fallback.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/shared/types/api.ts

@@ -38,6 +38,8 @@ export interface ListIssuesParams {
 export interface ListIssuesResponse {
   issues: Issue[];
   total: number;
+  /** True total of done issues in the workspace (for load-more pagination). Not returned by backend API — set by the frontend query function. */
+  doneTotal?: number;
 }
 
 export interface UpdateMeRequest {