Fix type errors

frontend/src/components/tools/merge/MergeSettings.test.tsx

@@ -19,6 +19,7 @@ describe('MergeSettings', () => {
   const defaultParameters: MergeParameters = {
     removeDigitalSignature: false,
     generateTableOfContents: false,
+    processingMode: 'backend',
   };
 
   const mockOnParameterChange = vi.fn();

frontend/src/hooks/tools/merge/useMergeOperation.test.ts

@@ -68,7 +68,8 @@ describe('useMergeOperation', () => {
     ];
     const parameters: MergeParameters = {
       removeDigitalSignature: true,
-      generateTableOfContents: false
+      generateTableOfContents: false,
+      processingMode: 'backend'
     };
 
     const formData = config.buildFormData(parameters, mockFiles);
@@ -105,7 +106,8 @@ describe('useMergeOperation', () => {
     // Test case 1: All options disabled
     const params1: MergeParameters = {
       removeDigitalSignature: false,
-      generateTableOfContents: false
+      generateTableOfContents: false,
+      processingMode: 'backend'
     };
     const formData1 = config.buildFormData(params1, mockFiles);
     expect(formData1.get('removeCertSign')).toBe('false');
@@ -114,7 +116,8 @@ describe('useMergeOperation', () => {
     // Test case 2: All options enabled
     const params2: MergeParameters = {
       removeDigitalSignature: true,
-      generateTableOfContents: true
+      generateTableOfContents: true,
+      processingMode: 'backend'
     };
     const formData2 = config.buildFormData(params2, mockFiles);
     expect(formData2.get('removeCertSign')).toBe('true');

frontend/src/hooks/tools/split/useSplitOperation.ts

@@ -3,7 +3,7 @@ import { useTranslation } from 'react-i18next';
 import { ToolType, useToolOperation, ToolOperationConfig } from '../shared/useToolOperation';
 import { createStandardErrorHandler } from '../../../utils/toolErrorHandler';
 import { SplitParameters, defaultParameters } from './useSplitParameters';
-import { SPLIT_METHODS } from '../../../constants/splitConstants';
+import { SPLIT_METHODS, type SplitMethod} from '../../../constants/splitConstants';
 import { useToolResources } from '../shared/useToolResources';
 import { splitPdfClientSide } from '../../../utils/pdfOperations/split';
 import { validatePageNumbers } from '../../../utils/pageSelection';
@@ -87,8 +87,8 @@ export const splitOperationConfig = {
         SPLIT_METHODS.BY_PAGE_COUNT,
         SPLIT_METHODS.BY_DOC_COUNT,
         SPLIT_METHODS.BY_SIZE
-      ];
-      if (!browserMethods.includes(params.method)) return false;
+      ] as SplitMethod[];
+      if (!params.method || !browserMethods.includes(params.method)) return false;
 
       // Method-specific validation
       switch (params.method) {

frontend/src/utils/pdfOperations/merge.ts

@@ -5,7 +5,7 @@ import { createFileFromApiResponse } from '../fileResponseUtils';
 const PDF_MIME_TYPE = 'application/pdf';
 
 export async function mergePdfClientSide(
-  params: MergeParameters,
+  _params: MergeParameters, // Cant use params in browser implementation
   files: File[]
 ): Promise<File[]> {
   if (files.length === 0) {

frontend/src/utils/pdfOperations/split.ts

@@ -88,7 +88,6 @@ async function splitPdfBySize(
 
       const outputs: File[] = [];
       let currentDoc = await PDFDocument.create();
-      let currentPageStart = 0;
       let partIndex = 1;
 
       for (let i = 0; i < totalPages; i++) {
@@ -117,7 +116,7 @@ async function splitPdfBySize(
           currentDoc = await PDFDocument.create();
           const [pageToAdd] = await currentDoc.copyPages(sourcePdf, [i]);
           currentDoc.addPage(pageToAdd);
-          currentPageStart = i;
+
           partIndex++;
         }
       }