feat(chat): port chat widget components from Dart to React

src/app/chat/components/pwa-install-dialog.module.css

@@ -0,0 +1,78 @@
+/* PwaInstallDialog PWA 安装弹窗样式 */
+
+.overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.5);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 60;
+}
+
+.dialog {
+  width: calc(100% - 40px);
+  max-width: 360px;
+  background: var(--color-surface, #1f1a2e);
+  border-radius: var(--radius-lg, 12px);
+  padding: var(--spacing-5, 20px);
+  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
+  text-align: center;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+}
+
+.icon {
+  width: 64px;
+  height: 64px;
+  border-radius: 50%;
+  background: rgba(248, 77, 150, 0.2);
+  color: var(--color-accent, #f84d96);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 32px;
+  margin-bottom: var(--spacing-4, 16px);
+}
+
+.title {
+  font-size: var(--font-size-lg, 18px);
+  font-weight: 600;
+  margin: 0 0 var(--spacing-2, 8px);
+  color: var(--color-text-primary, #fff);
+}
+
+.content {
+  font-size: var(--font-size-sm, 14px);
+  line-height: 1.5;
+  color: var(--color-text-secondary, #9e9e9e);
+  margin: 0 0 var(--spacing-5, 20px);
+}
+
+.actions {
+  display: flex;
+  gap: var(--spacing-3, 12px);
+  width: 100%;
+}
+
+.btn {
+  flex: 1 1 auto;
+  height: 40px;
+  border: 0;
+  border-radius: var(--radius-md, 8px);
+  font-size: var(--font-size-base, 14px);
+  font-weight: 600;
+  cursor: pointer;
+}
+
+.btnSecondary {
+  background: transparent;
+  color: var(--color-text-primary, #fff);
+  border: 1px solid rgba(255, 255, 255, 0.2);
+}
+
+.btnPrimary {
+  background: var(--color-accent, #f84d96);
+  color: #fff;
+}