ISMIS Helper: cross-browser build, CI, PDF fixes, Chrome download fix

Squash merge of feat/ismis-helper into prod.

popup.html

@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <link rel="stylesheet" href="popup.css">
+</head>
+<body>
+  <header class="top">
+    <h1>ISMIS Helper</h1>
+    <div class="master">
+      <label class="switch">
+        <input type="checkbox" id="masterToggle">
+        <span class="slider"></span>
+      </label>
+      <span id="masterLabel">Enabled</span>
+    </div>
+  </header>
+
+  <section class="tab">
+    <h2>Profiles</h2>
+    <ul id="profileList" class="profile-list"></ul>
+    <button id="addProfile" class="btn">+ Add Profile</button>
+    <div id="profileForm" class="form" hidden>
+      <input id="pName" placeholder="Profile name">
+      <input id="pUsername" placeholder="Username">
+      <input id="pPassword" type="password" placeholder="Password">
+      <label class="row"><input type="checkbox" id="pEnabled"> Enabled</label>
+      <div class="btn-row">
+        <button id="saveProfile" class="btn primary">Save</button>
+        <button id="cancelProfile" class="btn">Cancel</button>
+      </div>
+    </div>
+  </section>
+
+  <section class="tab">
+    <h2>PDF Settings</h2>
+    <label class="row"><input type="checkbox" id="truncateToggle"> Truncate long course descriptions (official PDF style)</label>
+    <label class="row"><input type="checkbox" id="showYearToggle"> Show Year Level on the PDF</label>
+    <label class="row">Custom Year Level (optional):
+      <input type="text" id="customYear" placeholder="e.g. 3">
+    </label>
+    <p class="hint">Leave blank to use the scraped value (auto-adjusted in Summer).</p>
+  </section>
+
+  <script src="popup.js"></script>
+</body>
+</html>