feat: 小程序移除管理后台入口，新增admin-web前端项目

将管理后台功能从微信小程序中剥离，独立为Vue.js前端项目admin-web

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

admin-web/src/components/ImagePreviewHost.vue

@@ -0,0 +1,57 @@
+<template>
+  <transition name="fade">
+    <div v-if="visible" class="preview-mask" @click.self="close">
+      <div class="preview-stage">
+        <div class="preview-close" @click="close">×</div>
+        <div v-if="urls.length > 1" class="preview-nav preview-prev" @click="prev">‹</div>
+        <img class="preview-img" :src="currentUrl" alt="preview" />
+        <div v-if="urls.length > 1" class="preview-nav preview-next" @click="next">›</div>
+      </div>
+    </div>
+  </transition>
+</template>
+
+<script>
+export default {
+  name: 'ImagePreviewHost',
+  data() {
+    return {
+      visible: false,
+      urls: [],
+      index: 0
+    }
+  },
+  computed: {
+    currentUrl() {
+      return this.urls[this.index] || ''
+    }
+  },
+  methods: {
+    open({ urls, current }) {
+      this.urls = Array.isArray(urls) ? urls.slice() : [urls]
+      const idx = this.urls.indexOf(current)
+      this.index = idx >= 0 ? idx : 0
+      this.visible = true
+      document.addEventListener('keydown', this.handleKey)
+    },
+    close() {
+      this.visible = false
+      document.removeEventListener('keydown', this.handleKey)
+    },
+    prev() {
+      this.index = (this.index - 1 + this.urls.length) % this.urls.length
+    },
+    next() {
+      this.index = (this.index + 1) % this.urls.length
+    },
+    handleKey(e) {
+      if (e.key === 'Escape') this.close()
+      else if (e.key === 'ArrowLeft') this.prev()
+      else if (e.key === 'ArrowRight') this.next()
+    }
+  },
+  beforeDestroy() {
+    document.removeEventListener('keydown', this.handleKey)
+  }
+}
+</script>