add flutter quiz project code

scripts/extract-questions.js

@@ -0,0 +1,31 @@
+const fs = require('fs');
+const vm = require('vm');
+
+const html = fs.readFileSync('index.html', 'utf8');
+const start = html.indexOf('const questions');
+const arrStart = html.indexOf('[', start);
+let depth = 0, inStr = false, esc = false, end = -1;
+for (let i = arrStart; i < html.length; i++) {
+  const c = html[i];
+  if (inStr) {
+    if (esc) { esc = false; continue; }
+    if (c === '\\') { esc = true; continue; }
+    if (c === "'") inStr = false;
+    continue;
+  }
+  if (c === "'") { inStr = true; continue; }
+  if (c === '[') depth++;
+  else if (c === ']') { depth--; if (depth === 0) { end = i; break; } }
+}
+let src = html.slice(arrStart, end + 1);
+src = src.replace(/\/\/\s*=====[^']*?=====\s*/g, ' ');
+
+const questions = vm.runInNewContext(src);
+const withIds = questions.map((q, i) => ({ id: i + 1, ...q }));
+const data = {
+  sets: [{ id: 1, name: 'Dart & Flutter 学习测验', questions: withIds }],
+  nextSetId: 2,
+  nextQId: withIds.length + 1
+};
+fs.writeFileSync('questions.json', JSON.stringify(data, null, 2), 'utf8');
+console.log('已提取', withIds.length, '道题 -> questions.json');