Fix bugs found in full security and stability audit.

Harden artifact paths and fusion uploads, repair pool reconnect and login ID tracking, fix agent/fusion/frontend regressions, and refresh PROBLEMS.md with the full findings list.

server/web/src/pages/DashboardPage.tsx

@@ -128,6 +128,9 @@ export default function DashboardPage() {
     setBulkBusy(true);
     try {
       await api.sendBulkCommand(onlineIds, action);
+    } catch (err) {
+      console.error(err);
+      alert(err instanceof Error ? err.message : 'Bulk command failed');
     } finally {
       setBulkBusy(false);
     }
@@ -269,6 +272,8 @@ export default function DashboardPage() {
             filters={filters}
             onChange={setFilters}
             selectedCount={selectedIds.size}
+            filteredCount={filteredAgents.length}
+            onSelectAllFiltered={() => setSelectedIds(new Set(filteredAgents.map((a) => a.id)))}
             onBulkAction={handleBulkAction}
             bulkBusy={bulkBusy}
           />