feat(ui): ReplyPier 品牌、中文界面与前端构建产物

替换品牌文案与图标，补齐窄屏布局和加载失败提示，确认主要旅程可操作。

frontend/src/components/pwa/InstallPrompt.vue

@@ -0,0 +1,75 @@
+<!--
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<script setup lang="ts" name="InstallPrompt">
+import { computed } from 'vue'
+import { usePWAInstall } from '@/composables/usePWAInstall'
+import { isShopifyEmbedded } from '@/pwa/register'
+
+const { canInstall, needsManualInstall, promptInstall } = usePWAInstall()
+
+// Dashed hint card per the design: native prompt where supported, share-sheet
+// instructions on iOS, hidden when installed/unsupported/embedded.
+const visible = computed(() => !isShopifyEmbedded() && (canInstall.value || needsManualInstall.value))
+
+const handleClick = () => {
+  if (canInstall.value) promptInstall()
+}
+</script>
+
+<template>
+  <button v-if="visible" type="button" class="install-hint" @click="handleClick">
+    <svg viewBox="0 0 24 24" width="18" height="18" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round" class="install-icon" aria-hidden="true"><path d="M12 15V3m0 0L8 7m4-4l4 4"/><path d="M5 13v5a3 3 0 003 3h8a3 3 0 003-3v-5"/></svg>
+    <span class="install-text">
+      安装 ChatterMate —
+      <span v-if="needsManualInstall" class="install-sub">分享 → 添加到主屏幕</span>
+      <span v-else class="install-sub">像原生应用一样使用</span>
+    </span>
+  </button>
+</template>
+
+<style scoped>
+.install-hint {
+  display: flex;
+  align-items: center;
+  gap: 11px;
+  width: 100%;
+  padding: 13px 15px;
+  border-radius: 14px;
+  border: 1px dashed var(--o10);
+  background: var(--o03);
+  color: var(--text3);
+  font-family: var(--font-sans);
+  font-size: 12.5px;
+  line-height: 1.35;
+  text-align: left;
+  cursor: pointer;
+  transition: background-color var(--transition-fast);
+}
+
+.install-hint:hover {
+  background: var(--o05);
+}
+
+.install-icon {
+  color: var(--c-teal);
+  flex-shrink: 0;
+}
+
+.install-sub {
+  color: var(--muted);
+}
+</style>