Implement contract document download functionality and enhance clearance review status checks

- Added methods to assert clearance reviewable, finalizable, and uploadable statuses in the ContractClearanceService.
- Introduced a new endpoint in ContractsController for downloading contract PDFs.
- Implemented download functionality in the contracts service for both backoffice and portal applications.
- Updated UI components to include download buttons for contract PDFs in relevant pages.
- Enhanced contract request and view pages to support contract document downloads.

apps/edr-freight-web/backoffice/src/components/contracts/ContractSignSuccessModal.tsx

@@ -0,0 +1,43 @@
+import { Button, Group, Modal, Stack, Text, ThemeIcon } from "@mantine/core";
+import { CheckCircle2 } from "lucide-react";
+
+export interface ContractSignSuccessModalProps {
+  opened: boolean;
+  onClose: () => void;
+  reference: string;
+  message?: string;
+  confirmLabel?: string;
+}
+
+export function ContractSignSuccessModal({
+  opened,
+  onClose,
+  reference,
+  message = "The contract has been signed and recorded.",
+  confirmLabel = "Back to contract request",
+}: ContractSignSuccessModalProps) {
+  return (
+    <Modal
+      opened={opened}
+      onClose={onClose}
+      title="Contract signed successfully"
+      centered
+      radius="lg"
+    >
+      <Stack gap="md" align="center" ta="center">
+        <ThemeIcon size={56} radius="xl" color="edr-green" variant="light">
+          <CheckCircle2 size={28} />
+        </ThemeIcon>
+        <Text fw={600}>{reference}</Text>
+        <Text size="sm" c="dimmed">
+          {message}
+        </Text>
+        <Group justify="center" mt="xs">
+          <Button color="edr-green" onClick={onClose}>
+            {confirmLabel}
+          </Button>
+        </Group>
+      </Stack>
+    </Modal>
+  );
+}