fix: use blob URL for Firefox downloads (data: URLs are access-denied)

Firefox rejects data: URLs in browser.downloads.download with
"Access denied for URL data:...", breaking the PDF export. Build the
download URL per-browser: a blob: object URL where URL.createObjectURL
exists (Firefox background page), falling back to the base64 data: URL
for Chrome MV3 service workers (no createObjectURL).

Bump version to 1.3.0.

background.js

@@ -10,11 +10,19 @@ function errMsg(err) {
   return String((err && err.message) || err);
 }
 
-// Build a download URL from PDF bytes. Chrome MV3 runs the background as a
+// Build a download URL from PDF bytes. Firefox's background is a real page
-// service worker, where URL.createObjectURL is NOT available, so we use a
+// (URL.createObjectURL available) and supports blob: URLs in downloads.
-// base64 data URL (works in both Firefox and Chrome). PDFs here are small
+// Chrome MV3 runs the background as a service worker where URL.createObjectURL
-// (~150KB), well within data-URL length limits.
+// is NOT available, but its downloads API accepts base64 data: URLs.
-function pdfDataUrl(bytes) {
+// Firefox rejects data: URLs in browser.downloads.download with
+// "Access denied for URL data:...", so pick per-browser.
+function buildDownloadUrl(bytes) {
+  if (typeof URL !== 'undefined' && typeof URL.createObjectURL === 'function') {
+    const blob = new Blob([bytes], { type: 'application/pdf' });
+    return URL.createObjectURL(blob);
+  }
+  // Fallback: Chrome MV3 service worker. PDFs here are small (~150KB), well
+  // within data-URL length limits.
   let binary = '';
   const chunk = 0x8000;
   for (let i = 0; i < bytes.length; i += chunk) {
@@ -45,9 +53,9 @@ function formatPeriod(period) {
 
 async function generatePdf(data) {
   const bytes = await ISMIStools.buildStudyLoadPdf(data);
-  // Chrome MV3 background is a service worker (no URL.createObjectURL), so we
+  // Firefox accepts blob: object URLs; Chrome MV3 service worker has no
-  // use a base64 data URL that works in both browsers.
+  // URL.createObjectURL, so it falls back to a base64 data: URL there.
-  const url = pdfDataUrl(bytes);
+  const url = buildDownloadUrl(bytes);
   const header = data.header || {};
   const year = parseInt(data.year, 10);
   const period = formatPeriod(data.period || header.semester || '');

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "ISMIS Helper",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "Auto-login, auto-accept privacy policy, and Study Load PDF for the USC ISMIS portal.",
   "permissions": ["storage", "downloads"],
   "host_permissions": ["https://ismis.usc.edu.ph/*"],