Enable ESLint no-unused-vars rule (#4367)

# Description of Changes
Enable ESLint [no-unused-vars
rule](https://typescript-eslint.io/rules/no-unused-vars/)

frontend/src/services/enhancedPDFProcessingService.ts

@@ -1,5 +1,4 @@
-import * as pdfjsLib from 'pdfjs-dist';
-import { ProcessedFile, ProcessingState, PDFPage, ProcessingStrategy, ProcessingConfig, ProcessingMetrics } from '../types/processing';
+import { ProcessedFile, ProcessingState, PDFPage, ProcessingConfig, ProcessingMetrics } from '../types/processing';
 import { ProcessingCache } from './processingCache';
 import { FileHasher } from '../utils/fileHash';
 import { FileAnalyzer } from './fileAnalyzer';
@@ -355,7 +354,7 @@ export class EnhancedPDFProcessingService {
    */
   private async processMetadataOnly(
     file: File,
-    config: ProcessingConfig,
+    _config: ProcessingConfig,
     state: ProcessingState
   ): Promise<ProcessedFile> {
     const arrayBuffer = await file.arrayBuffer();
@@ -510,7 +509,7 @@ export class EnhancedPDFProcessingService {
    */
   clearAllProcessing(): void {
     // Cancel all ongoing processing
-    this.processing.forEach((state, key) => {
+    this.processing.forEach((state) => {
       if (state.cancellationToken) {
         state.cancellationToken.abort();
       }

frontend/src/services/fileAnalyzer.ts

@@ -128,7 +128,7 @@ export class FileAnalyzer {
    * Estimate processing time based on file characteristics and strategy
    */
   private static estimateProcessingTime(
-    fileSize: number,
+    _fileSize: number,
     pageCount: number = 0,
     strategy: ProcessingStrategy
   ): number {
@@ -234,7 +234,7 @@ export class FileAnalyzer {
       const headerString = String.fromCharCode(...headerBytes);
 
       return headerString.startsWith('%PDF-');
-    } catch (error) {
+    } catch {
       return false;
     }
   }

frontend/src/services/fileProcessingService.ts

@@ -4,7 +4,6 @@
  * Called when files are added to FileContext, before any view sees them
  */
 
-import * as pdfjsLib from 'pdfjs-dist';
 import { generateThumbnailForFile } from '../utils/thumbnailUtils';
 import { pdfWorkerManager } from './pdfWorkerManager';
 import { FileId } from '../types/file';

frontend/src/services/fileStorage.ts

@@ -496,7 +496,7 @@ class FileStorageService {
   async updateThumbnail(id: FileId, thumbnail: string): Promise<boolean> {
     const db = await this.getDatabase();
 
-    return new Promise((resolve, reject) => {
+    return new Promise((resolve, _reject) => {
       try {
         const transaction = db.transaction([this.storeName], 'readwrite');
         const store = transaction.objectStore(this.storeName);

frontend/src/services/pdfExportService.ts

@@ -31,7 +31,7 @@ export class PDFExportService {
       const originalPDFBytes = await pdfDocument.file.arrayBuffer();
       const sourceDoc = await PDFLibDocument.load(originalPDFBytes);
       const blob = await this.createSingleDocument(sourceDoc, pagesToExport);
-      const exportFilename = this.generateFilename(filename || pdfDocument.name, selectedOnly, false);
+      const exportFilename = this.generateFilename(filename || pdfDocument.name);
 
       return { blob, filename: exportFilename };
     } catch (error) {
@@ -62,7 +62,7 @@ export class PDFExportService {
       }
 
       const blob = await this.createMultiSourceDocument(sourceFiles, pagesToExport);
-      const exportFilename = this.generateFilename(filename || pdfDocument.name, selectedOnly, false);
+      const exportFilename = this.generateFilename(filename || pdfDocument.name);
 
       return { blob, filename: exportFilename };
     } catch (error) {
@@ -183,7 +183,7 @@ export class PDFExportService {
   /**
    * Generate appropriate filename for export
    */
-  private generateFilename(originalName: string, selectedOnly: boolean, appendSuffix: boolean): string {
+  private generateFilename(originalName: string): string {
     const baseName = originalName.replace(/\.pdf$/i, '');
     return `${baseName}.pdf`;
   }
@@ -210,7 +210,7 @@ export class PDFExportService {
   /**
    * Download multiple files as a ZIP
    */
-  async downloadAsZip(blobs: Blob[], filenames: string[], zipFilename: string): Promise<void> {
+  async downloadAsZip(blobs: Blob[], filenames: string[]): Promise<void> {
     blobs.forEach((blob, index) => {
       setTimeout(() => {
         this.downloadFile(blob, filenames[index]);

frontend/src/services/pdfWorkerManager.ts

@@ -93,7 +93,7 @@ class PDFWorkerManager {
       if (loadingTask) {
         try {
           loadingTask.destroy();
-        } catch (destroyError) {
+        } catch {
           // Ignore errors
         }
       }
@@ -110,7 +110,7 @@ class PDFWorkerManager {
         pdf.destroy();
         this.activeDocuments.delete(pdf);
         this.workerCount = Math.max(0, this.workerCount - 1);
-      } catch (error) {
+      } catch {
         // Still remove from tracking even if destroy failed
         this.activeDocuments.delete(pdf);
         this.workerCount = Math.max(0, this.workerCount - 1);
@@ -166,7 +166,7 @@ class PDFWorkerManager {
     this.activeDocuments.forEach(pdf => {
       try {
         pdf.destroy();
-      } catch (error) {
+      } catch {
         // Ignore errors
       }
     });

frontend/src/services/zipFileService.ts

@@ -277,7 +277,7 @@ export class ZipFileService {
              bytes[2] === 0x44 && // D
              bytes[3] === 0x46 && // F
              bytes[4] === 0x2D;   // -
-    } catch (error) {
+    } catch {
       return false;
     }
   }
@@ -324,7 +324,7 @@ export class ZipFileService {
       await zip.loadAsync(file);
 
       // Check if any files are encrypted
-      for (const [filename, zipEntry] of Object.entries(zip.files)) {
+      for (const [_filename, zipEntry] of Object.entries(zip.files)) {
         if (zipEntry.options?.compression === 'STORE' && getData(zipEntry)?.compressedSize === 0) {
           // This might indicate encryption, but JSZip doesn't provide direct encryption detection
           // We'll handle this in the extraction phase