feat: implement PDF attachment extraction functionality with web worker support

- Added a new worker script to handle extraction of embedded attachments from PDF files.
- Created TypeScript definitions for the message structure and response types.
- Updated the main extraction logic to utilize the worker for improved performance and responsiveness.
- Integrated the extraction feature into the UI, allowing users to extract attachments as a ZIP file.
- Enhanced error handling and user feedback during the extraction process.

public/workers/extract-attachments.worker.js

@@ -0,0 +1,106 @@
+self.importScripts('/coherentpdf.browser.min.js');
+
+function extractAttachmentsFromPDFsInWorker(fileBuffers, fileNames) {
+  try {
+    const allAttachments = [];
+    const totalFiles = fileBuffers.length;
+    
+    for (let i = 0; i < totalFiles; i++) {
+      const buffer = fileBuffers[i];
+      const fileName = fileNames[i];
+      const uint8Array = new Uint8Array(buffer);
+      
+      let pdf;
+      try {
+        pdf = coherentpdf.fromMemory(uint8Array, '');
+      } catch (error) {
+        console.warn(`Failed to load PDF: ${fileName}`, error);
+        continue;
+      }
+
+      coherentpdf.startGetAttachments(pdf);
+      const attachmentCount = coherentpdf.numberGetAttachments();
+
+      if (attachmentCount === 0) {
+        console.warn(`No attachments found in ${fileName}`);
+        coherentpdf.deletePdf(pdf);
+        continue;
+      }
+
+      const baseName = fileName.replace(/\.pdf$/i, '');
+      for (let j = 0; j < attachmentCount; j++) {
+        try {
+          const attachmentName = coherentpdf.getAttachmentName(j);
+          const attachmentPage = coherentpdf.getAttachmentPage(j);
+          const attachmentData = coherentpdf.getAttachmentData(j);
+
+          let uniqueName = attachmentName;
+          let counter = 1;
+          while (allAttachments.some(att => att.name === uniqueName)) {
+            const nameParts = attachmentName.split('.');
+            if (nameParts.length > 1) {
+              const extension = nameParts.pop();
+              uniqueName = `${nameParts.join('.')}_${counter}.${extension}`;
+            } else {
+              uniqueName = `${attachmentName}_${counter}`;
+            }
+            counter++;
+          }
+
+          if (attachmentPage > 0) {
+            uniqueName = `${baseName}_page${attachmentPage}_${uniqueName}`;
+          } else {
+            uniqueName = `${baseName}_${uniqueName}`;
+          }
+
+          allAttachments.push({
+            name: uniqueName,
+            data: attachmentData.buffer.slice(0)
+          });
+        } catch (error) {
+          console.warn(`Failed to extract attachment ${j} from ${fileName}:`, error);
+        }
+      }
+
+      coherentpdf.endGetAttachments();
+      coherentpdf.deletePdf(pdf);
+    }
+
+    if (allAttachments.length === 0) {
+      self.postMessage({
+        status: 'error',
+        message: 'No attachments were found in the selected PDF(s).'
+      });
+      return;
+    }
+    
+    const response = {
+      status: 'success',
+      attachments: []
+    };
+
+    const transferBuffers = [];
+    for (const attachment of allAttachments) {
+      response.attachments.push({
+        name: attachment.name,
+        data: attachment.data
+      });
+      transferBuffers.push(attachment.data);
+    }
+
+    self.postMessage(response, transferBuffers);
+  } catch (error) {
+    self.postMessage({
+      status: 'error',
+      message: error instanceof Error
+        ? error.message
+        : 'Unknown error occurred during attachment extraction.'
+    });
+  }
+}
+
+self.onmessage = (e) => {
+  if (e.data.command === 'extract-attachments') {
+    extractAttachmentsFromPDFsInWorker(e.data.fileBuffers, e.data.fileNames);
+  }
+};