Sync Canvas LMS export feature + refreshed Settings screenshot

Brings the share build up to date with the main project: QTI .zip export
and optional direct Canvas API push, plus the Canvas settings card.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/store.js

@@ -31,6 +31,12 @@ export const DEFAULT_SETTINGS = {
     maxSourceChars: 24000,
     verification: true,
   },
+  // Optional: push quizzes straight into a Canvas course (lib/canvas/api.js).
+  // baseUrl is the institution's Canvas, token is a personal access token.
+  canvas: {
+    baseUrl: "",
+    token: "",
+  },
 };
 
 function emptyDb() {
@@ -69,6 +75,7 @@ export function mergeSettings(saved) {
   }
   out.generation = { ...base.generation, ...(saved.generation || {}) };
   out.profile = { ...base.profile, ...(saved.profile || {}) };
+  out.canvas = { ...base.canvas, ...(saved.canvas || {}) };
   return out;
 }