feat: 添加PWA manifest、更新品牌图标配色、添加打印样式

frontend/src/styles/global.css

@@ -401,3 +401,65 @@ html, body, #app {
   background: var(--primary-bg);
   color: var(--primary);
 }
+
+/* ===== Print Styles ===== */
+@media print {
+  .zj-sidebar,
+  .zj-header,
+  .floating-composer,
+  .create-topbar,
+  .result-actions,
+  .toolbar-actions,
+  .canvas-toolbar,
+  .prompt-toolbar,
+  .task-toolbar,
+  .quick-nav,
+  .help-footer,
+  .el-message,
+  .el-dialog,
+  .el-overlay,
+  .back-btn,
+  .action-btn,
+  .gen-btn,
+  .tool-btn,
+  .save-btn,
+  .new-task,
+  .points-banner,
+  .sidebar-bottom,
+  .filter-panel button,
+  .card-actions,
+  .saved-actions,
+  .prompt-actions,
+  .settings-row,
+  .material-row,
+  .input-settings,
+  .gen-input-section,
+  .guide-section,
+  .loading-section,
+  .saved-section,
+  nav,
+  aside,
+  header,
+  footer { display: none !important; }
+
+  body { background: #fff !important; }
+  .page-container,
+  .create-body,
+  .create-page,
+  .canvas-scroll,
+  .result-section,
+  .animation-preview,
+  .mm-canvas-panel { width: 100% !important; max-width: 100% !important; margin: 0 !important; padding: 0 !important; box-shadow: none !important; border: none !important; }
+  .zj-home,
+  .create-page,
+  .page-container { padding: 0 !important; }
+  .html-preview-frame,
+  .preview-iframe { width: 100% !important; height: auto !important; min-height: 500px !important; page-break-inside: avoid; }
+  * { color: #000 !important; }
+  a { text-decoration: none !important; }
+  .el-card,
+  .el-table { box-shadow: none !important; border: 1px solid #ddd !important; }
+  h1, h2, h3 { page-break-after: avoid; }
+  .courseware-page,
+  .exam-question { page-break-inside: avoid; }
+}