add company stamp upload functionality for contract signing

- Introduced StampUpload component for uploading company stamp images.
- Integrated stamp upload in contract signing modal, supporting PNG and JPG formats.
- Implemented validation for file type and size (max 5 MB).
- Added visual feedback for drag-and-drop functionality.
- Updated contract-related pages to handle duplicate contract alerts and pricing notices.
- Enhanced contract expiry management with a nightly sweep service.
- Added unit tests for new features and updated existing tests for contract handling.

apps/edr-freight-web/backoffice/src/services/contracts.service.ts

@@ -109,6 +109,7 @@ export interface ContractView {
     signerDisplayName: string;
     signedAt: string;
     signatureImageUrl?: string | null;
+    stampImageUrl?: string | null;
   }>;
   savedSignature?: {
     signerDisplayName: string;
@@ -119,6 +120,8 @@ export interface ContractView {
 export interface SignContractPayload {
   role: "CUSTOMER" | "STAFF";
   signatureImageBase64: string;
+  /** Company stamp/seal image; required to sign a contract. */
+  stampImageBase64?: string;
   signerDisplayName: string;
   consentText?: string;
 }