swarm-ui: add the custom issue-report page

New /issues route: a sortable, filterable table over open issues across
every repo that has one -- repo picker (default: no filter, every repo
combined), hide-blocked toggle, and a label multi-select, consuming
swarm-controller's GET /api/repos + GET /api/issue-report / GET
/api/repos/{org}/{repo}/issue-report (see hyperhive#3831 for the row
shape). blocked and depended_on_by_count arrive pre-resolved per row --
this page does no dependency-graph walking of its own, just sort/filter
over what it's given. Default sort is depended_on_by_count descending,
matching mara's framing of the report's headline ordering.

Widened Table's TableColumn.header from string to ComponentChildren so
a column can carry a real clickable sort-toggle button instead of
forking a second table primitive for this one page.

frontend/packages/swarm-ui/src/App.tsx

@@ -6,6 +6,7 @@ import { AgentsPage } from './pages/AgentsPage.js';
 import { ComponentsPage } from './pages/ComponentsPage.js';
 import { JobsPage } from './pages/JobsPage.js';
 import { HivesPage } from './pages/HivesPage.js';
+import { IssueReportPage } from './pages/IssueReportPage.js';
 import { Panel } from './ui/panel/Panel.js';
 
 function NotFound() {
@@ -23,6 +24,7 @@ export function App() {
         <Route path="/" component={HivesPage} />
         <Route path="/agents" component={AgentsPage} />
         <Route path="/jobs" component={JobsPage} />
+        <Route path="/issues" component={IssueReportPage} />
         <Route path="/components" component={ComponentsPage} />
         <Route component={NotFound} />
       </Switch>