feat(aigc): add travel postcard AIGC feature

Add complete travel postcard AIGC creation workflow including:
- New AIGC pages: template selection home, result detail, and history records
- Reusable UI components: template card, flow steps, result preview, action buttons, record lists
- Static assets including template images, fonts and styles
- Updated TopNavBar component to support menu button alignment
- Register new AIGC page routes in pages.json
- Add mock data for templates, user records and result details

src/pages-aigc/home/components/TemplateCarousel/styles/index.scss

@@ -0,0 +1,86 @@
+.template-carousel {
+  max-width: 100vw;
+  overflow: hidden;
+}
+
+.template-heading {
+  height: 34px;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin: 0 16px 20px;
+}
+
+.template-heading-title,
+.template-heading-subtitle {
+  display: block;
+}
+
+.template-heading-title {
+  color: #172033;
+  font-size: 16px;
+  line-height: 21px;
+  font-weight: 900;
+}
+
+.template-heading-subtitle {
+  margin-top: 1px;
+  color: #7a8596;
+  font-size: 10px;
+  line-height: 13px;
+  font-weight: 800;
+}
+
+.template-heading-badge {
+  height: 26px;
+  display: inline-flex;
+  align-items: center;
+  padding: 0 10px;
+  border-radius: 999px;
+  background: rgba(32, 207, 117, 0.12);
+  color: #10a765;
+  font-size: 11px;
+  line-height: 26px;
+  font-weight: 900;
+}
+
+.template-rail {
+  max-width: 100vw;
+  height: 560px;
+  overflow-x: auto;
+  overflow-y: hidden;
+  scrollbar-width: none;
+}
+
+.template-rail::-webkit-scrollbar {
+  display: none;
+}
+
+.template-track {
+  display: inline-flex;
+  align-items: flex-start;
+  gap: 12px;
+  height: 560px;
+  padding: 0 41px 0 16px;
+  box-sizing: border-box;
+}
+
+.template-dots {
+  height: 14px;
+  display: flex;
+  justify-content: center;
+  gap: 6px;
+  margin-top: 5px;
+}
+
+.template-dot {
+  width: 6px;
+  height: 6px;
+  border-radius: 999px;
+  background: rgba(23, 32, 51, 0.16);
+}
+
+.template-dot.is-active {
+  width: 18px;
+  background: #20cf75;
+}