Fix state persistence when popup is closed

- Add 'dismissed' status to prevent dismissed PDFs from reappearing
- Persist PDFs discovered from current tab and recent downloads via background
- Add dismissPDF function that marks PDFs as dismissed instead of removing
- Dismissed PDFs are kept for 7 days for duplicate detection, then cleaned up
- Completed items (sent/canceled) can still be fully removed
- Add addPDF message handler to service worker for popup-discovered PDFs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/background/service-worker.ts

@@ -11,6 +11,7 @@ import {
   getAllPDFs,
   getPendingPDFs,
   updatePDFStatus,
+  dismissPDF,
   removePDF,
   cleanupOldEntries,
   PDFStatus,
@@ -129,6 +130,19 @@ chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
     return true;
   }
 
+  // Add a PDF to the queue (from popup discovery)
+  if (request.action === 'addPDF') {
+    addPDF(request.pdf).then(entry => {
+      if (entry) {
+        console.log('[Service Worker] PDF added via message:', entry.filename);
+      }
+      return updateBadge().then(() => entry);
+    }).then(entry => {
+      sendResponse({ entry });
+    });
+    return true;
+  }
+
   // Legacy: Get only actionable PDFs
   if (request.action === 'getPDFQueue') {
     getPendingPDFs().then(entries => {
@@ -148,6 +162,15 @@ chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
     return true;
   }
 
+  if (request.action === 'dismissPDF') {
+    dismissPDF(request.id).then(() => {
+      return updateBadge();
+    }).then(() => {
+      sendResponse({ success: true });
+    });
+    return true;
+  }
+
   if (request.action === 'removePDF') {
     removePDF(request.id).then(() => {
       return updateBadge();