feat(release): v0.2.0 — batch 837 export, ClaimCard, theme tokens

Backend:

- New POST /api/batches/{id}/export-837: regenerate X12 837 files
  for a list of claim_ids into a ZIP using HCPF file naming standards,
  with a unique interchange/group control number per export. Wire
  the clearhouse Loop 1000A (NM1*41 + PER) and per-payer receiver
  (NM1*40) blocks so the serializer no longer falls back to
  CYCLONE / RECEIVER placeholders.
- /api/parse-837 and /api/parse-835 now surface the server-side
  batch_id in both JSON and NDJSON response shapes so the frontend
  can hit batch-scoped endpoints without an extra listBatches
  round-trip.
- Filename helpers and the 837 serializer updated to match the new
  HCPF envelope; tests cover batch export, parse batch_id, and the
  serializer's control-number uniqueness guarantee.

Frontend:
- New shared components: ClaimCard, ClaimCard837, DominantKpiCard,
  EditorialNote, ExportBar, TickerTape, and a charts/ set
  (BarChart, HBarChart, SegmentedBar, AgingBars).
- New useBatchExport hook driving ExportBar's download flow against
  the new endpoint.
- ClaimDrawer, Lane, and Layout migrated from raw CSS-variable
  colors to Tailwind theme tokens (bg-card, text-foreground,
  border/60, etc.) for consistency with the rest of the instrument
  chrome; the active tab indicator gains a subtle accent glow.
- Upload, Inbox, Batches, BatchDiff, Reconciliation, and Acks pages
  reworked to compose the new shared components and consume the new
  batch-scoped API surface (notably ExportBar wired into Batches).

Tooling / Docs:
- Add audit-uiux.mjs and a docs/goodclaim.x12 sample fixture.
- Update ClaimDrawer testids and add coverage for the new
  components and the useBatchExport hook.

Rolls up into the v0.2.0 release tag.

src/components/Layout.tsx

@@ -24,6 +24,24 @@ export function Layout() {
   return (
     <div className="relative min-h-screen z-10">
       <SkipLink />
+      {/* Ambient page halo — a soft, fixed radial that creates a
+          subtle lighter zone behind the page content (centered
+          just below the top bar). Pure decoration; pointer-events
+          disabled so it never intercepts clicks. Two layered
+          radials: a neutral softbox centered above the page
+          header, and a cool accent in the upper-right that
+          mirrors the body::before composition. The halo sits
+          behind everything else (z-0 inside the z-10 root). */}
+      <div
+        aria-hidden
+        className="pointer-events-none fixed inset-x-0 top-0 z-0 h-[70vh]"
+        style={{
+          background: `
+            radial-gradient(ellipse 55% 30% at 50% 6%, hsla(220, 32%, 30%, 0.16), transparent 70%),
+            radial-gradient(ellipse 35% 25% at 82% 10%, hsla(212, 70%, 60%, 0.10), transparent 65%)
+          `,
+        }}
+      />
       <div
         className="fixed top-0 left-0 right-0 z-50 h-px overflow-hidden pointer-events-none transition-opacity duration-200"
         style={{ opacity: showScan ? 1 : 0 }}