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/detail/components/ResultActions/index.vue

@@ -0,0 +1,14 @@
+<template>
+  <view class="result-actions">
+    <view class="result-action is-primary" @tap="emit('save')">保存图片</view>
+    <view class="result-action is-secondary" @tap="emit('share')">分享好友</view>
+  </view>
+</template>
+
+<script setup>
+const emit = defineEmits(["save", "share"]);
+</script>
+
+<style scoped lang="scss">
+@import "./styles/index.scss";
+</style>