Fix CSV import failure when DataSource column is missing

Set default dataSource in frontend CSV parser before sending to backend:
  - MANUAL for FEE/INTEREST/LIABILITY types
  - YAHOO for other types (BUY/SELL/DIVIDEND)

  Fixes DTO validation error that occurred before backend's default dataSource
  assignment could execute.

apps/client/src/app/services/import-activities.service.ts

@@ -58,9 +58,19 @@ export class ImportActivitiesService {
 
     for (const [index, item] of content.entries()) {
       const currency = this.parseCurrency({ content, index, item });
-      const dataSource = this.parseDataSource({ item });
-      const symbol = this.parseSymbol({ content, index, item });
       const type = this.parseType({ content, index, item });
+      const symbol = this.parseSymbol({ content, index, item });
+      let dataSource = this.parseDataSource({ item });
+
+      // Set default dataSource if not provided in CSV
+      if (!dataSource) {
+        if (['FEE', 'INTEREST', 'LIABILITY'].includes(type)) {
+          dataSource = DataSource.MANUAL;
+        } else {
+          // For other types, try to determine from symbol or default to YAHOO
+          dataSource = DataSource.YAHOO;
+        }
+      }
 
       activities.push({
         currency,