perf(panel): kanban virtualization + row memoization + scorecards batch endpoint (#594)

* perf(panel): kanban virtualization + row memoization + scorecards batch endpoint

The audit's remaining phases: the kanban card lists render through
@tanstack/react-virtual windows (columns are the dnd drop targets, cards
only drag — no sortable conflict) with memoized columns/cards and a
stabilized handleAction; the task table's desktop row and mobile card are
extracted and memoized (the table itself already client-paginates to 100).
Backend: the per-member scorecard N+1 (~20 requests x 3 queries per poll)
collapses into GET /dashboard/metrics/members backed by
get_all_member_scorecards with grouped rollup/overlay SQL shared with the
single-agent path.

* test(metrics): shared-DB-safe scorecard tests — unique seeds, delta assertions

The two new batch-scorecard tests assumed a private DB: fixed ceo/system
slugs collided with other tests' seeds (ix_agents_slug) and a global
exactly-one CEO lookup + exact roster count broke in the one-process
suite. Unique slugs, subset/disjoint assertions, dead count constant
dropped.

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Co-authored-by: Renn F <rennf93@users.noreply.github.com>

panel/package.json

@@ -37,6 +37,7 @@
     "@radix-ui/react-tooltip": "^1.2.12",
     "@tailwindcss/typography": "^0.5.20",
     "@tanstack/react-query": "^5.101.2",
+    "@tanstack/react-virtual": "3.14.6",
     "axios": "^1.16.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",