feat(eoi): signed-EOI hero + send-signed-copy; fix search dropdown z-order

- EOI tab: when an EOI is already signed and none is in flight, lead with a
  SignedEoiCard (preview + download + send-to-client) instead of the big
  "Generate EOI" empty state; quiet "Generate new EOI" remains for re-issue
- history rows + hero gain a "Send to client" action — POST
  /api/v1/documents/[id]/send-signed-copy emails the deal's client the
  finalized signed PDF (sendSignedCopyToClient reuses sendSigningCompleted),
  guarded by a confirm
- topbar: header gets z-30 so the global search dropdown paints above page
  content (charts/tables were bleeding through — header + main are sibling
  normal-flow boxes, so the dropdown's own z-50 couldn't win cross-context).
  Stays below the z-50 modal tier.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/api/v1/documents/[id]/send-signed-copy/route.ts

@@ -0,0 +1,21 @@
+import { NextResponse } from 'next/server';
+
+import { withAuth, withPermission } from '@/lib/api/helpers';
+import { errorResponse } from '@/lib/errors';
+import { sendSignedCopyToClient } from '@/lib/services/documents.service';
+
+/**
+ * Manually (re)send the finalized signed PDF to the deal's client. Backs
+ * the "Send signed copy to client" affordance on the EOI tab + document
+ * detail. Same `documents.edit` gate as the reminder endpoint.
+ */
+export const POST = withAuth(
+  withPermission('documents', 'edit', async (_req, ctx, params) => {
+    try {
+      const result = await sendSignedCopyToClient(params.id!, ctx.portId);
+      return NextResponse.json({ data: result });
+    } catch (error) {
+      return errorResponse(error);
+    }
+  }),
+);