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.

packages/types/src/freight/contracts.ts

@@ -184,6 +184,8 @@ export interface IContractSignature {
   role: ContractSignatureRole;
   signerDisplayName: string;
   signatureFileId?: string | null;
+  /** Company stamp/seal image, required for the CUSTOMER and STAFF parties. */
+  stampFileId?: string | null;
   consentText?: string | null;
   signedAt: string;
 }