feat: Features架构迁移 - P0和P1部分完成

## 完成的工作

### P0: 基础设施准备
- 创建 features/ 和 shared/ 目录结构
- 迁移共享资源：API基础设施、工具函数、类型定义
- 迁移通用composables：useMoney, useSmsCountdown, usePricingCalculator
- 迁移全局样式文件
- 建立模块化导出系统

### P1.1: 钱包模块 (wallet)
- 迁移 API: wallet.ts
- 迁移 Views: WalletView.vue
- 新增 Composable: useWallet.ts (封装钱包状态管理)
- 更新导入路径到 shared/

### P1.2: 聊天模块 (chats)
- 迁移 API: chats.ts
- 迁移 Views: ChatView, MessagesView (桌面+移动)
- 迁移 Composables: useChatSSE.ts
- 迁移 Components: ChatAttachmentImage.vue
- 更新导入路径到 shared/

## 技术改进
- 修复 shared/composables 导出问题 (default → 命名导出)
- 修复 shared/api/client.ts 类型导入路径
- 建立清晰的模块边界和导出规范

## 文档
- 添加完整的迁移计划文档
- 添加进度跟踪文档

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/shared/components/business/ChatAttachmentImage.vue

@@ -0,0 +1,90 @@
+<script setup lang="ts">
+import { onBeforeUnmount, ref, watch } from 'vue'
+import { fetchAdminFileBlob, fetchFileBlobByURL } from '@/api/files'
+
+const props = defineProps<{
+  source: string
+  admin?: boolean
+}>()
+
+const objectURL = ref('')
+const failed = ref(false)
+
+function extractObjectKey(value: string) {
+  try {
+    const parsed = new URL(value, window.location.origin)
+    return parsed.searchParams.get('key') || ''
+  } catch {
+    return ''
+  }
+}
+
+function revokeCurrentURL() {
+  if (!objectURL.value) return
+  URL.revokeObjectURL(objectURL.value)
+  objectURL.value = ''
+}
+
+async function loadImage() {
+  revokeCurrentURL()
+  failed.value = false
+  if (!props.source) {
+    failed.value = true
+    return
+  }
+  try {
+    const key = extractObjectKey(props.source)
+    const blob = props.admin && key
+      ? await fetchAdminFileBlob(key)
+      : await fetchFileBlobByURL(props.source)
+    objectURL.value = URL.createObjectURL(blob)
+  } catch {
+    failed.value = true
+  }
+}
+
+function openImage() {
+  if (!objectURL.value) return
+  window.open(objectURL.value, '_blank')
+}
+
+watch(() => [props.source, props.admin] as const, loadImage, { immediate: true })
+
+onBeforeUnmount(revokeCurrentURL)
+</script>
+
+<template>
+  <button v-if="objectURL" class="chat-image-button" type="button" @click="openImage">
+    <img :src="objectURL" alt="聊天图片" loading="lazy" decoding="async">
+  </button>
+  <span v-else class="chat-image-fallback">{{ failed ? '图片加载失败' : '图片加载中' }}</span>
+</template>
+
+<style scoped>
+.chat-image-button {
+  display: block;
+  max-width: 220px;
+  padding: 0;
+  overflow: hidden;
+  border: 0;
+  border-radius: 8px;
+  background: transparent;
+  cursor: zoom-in;
+}
+
+.chat-image-button img {
+  display: block;
+  width: 100%;
+  max-height: 260px;
+  object-fit: cover;
+}
+
+.chat-image-fallback {
+  display: inline-block;
+  padding: 8px 10px;
+  border-radius: 8px;
+  background: #eef2f7;
+  color: #6b7280;
+  font-size: 12px;
+}
+</style>